Reasons Why Triathlon Event Order Is Swim Bike and Run

I got a request from a buddy on why a triathlon event order is Swim, followed by Bike and then by Run. Why can't it be in any other order, like - Bike, Run, Swim or Run, Swim Bike? I found the question to be very valid. More so for someone like me that believes in Triathlonism. I went into meditation and found a few possible answers. Before that, it could be worth it to understand how triathlon started.
A Short History of Triathlon
A check on Wikipedia points to the French for starting a multi-sports event in 1902. I have always believed the French are crazy people for a long time. Known as Les trois sports, it compromises running, cycling and canoeing (not verified if this is true) and there were record of what we now known as triathlon in the 1920s with swimming, cycling and running (though not in this order all the while) as a local sports event. Until the late 1930's, It is still a very "French sports".

Not a French

Fast forward to the 1970's. A group of US Military men in Hawaii got bored of their usual Physical Training and had too much time in their hands while having a few drinks with a few locals - They were debating if a runner or swimmer were fitter; and someone came in and say that the cyclist got to be the fittest with a high oxygen uptake. Of course none of them could agree to who is actually the fittest and that has given birth to modern triathlon - in fact, the argument lead to the birth of an Ultra distance triathlon known as Ironman Triathlon. A gruelling 2.4miles (or 3.8km) Swim, followed by a 112miles (or 180km) cycling and ends with a 26.2miles (or 42.2km) run. The winner of the race will then be known as Ironman. With that, modern (and painful) triathlon was born in Kona, Hawaii.
A triathlon race, however, are not limited to just the above distance. There are many variation and a more popular distance is known as the Olympic distance which usually consist of a 1.5km swim, 40km bike and a 10km run. Even that, the London Olympic has seen a variation to the distance by having a longer biking route due to existing route arrangement. 
But still, why Swim, Bike, and then Run?
I know, i still have not answered the question on why the sports is done in that order. From my years of racing and understanding how the sports is, i can offer two explanation : Safety and Triathletes' Abilities. lets look into each and see if i could make any sense.
1. Safety
Triathlon races typically starts in the morning. For shorter races, It could end as fast as an hour for a Sprint race (typically half of Olympic distance) to as long as 17hours for the Ultra distance Ironman race (totalling 140.2miles or 226kilometers). 

Out of water - SUPER happy.

The (at this point of time) normal triathlon starts with SWIM. Being the shortest league of the race which ranges anything a few hundred meters to 10kilometers (Ultraman Triathlon). Many people are not natural in water though we spent the first 9months of our life in the womb which is literally filled with liquid. So, by default that you are freshest and strongest in the morning, it is naturally that the "swim will not be a problem" and risk is at the lowest. 
The next league is CYCLING (ranges between a few kilometers to hundreds of kilometers), which technically starts to work the lower part of body. This will then be followed by RUNNING (anything from a couple of hundred meters to an ultra marathon of 84km), which again, utilises the lower part of the body. So, how is this relevant to the question of safety?

Maximum exposure to leg fatigue and merciless sun

As the race progresses, The body gets tired. More and more fatigue sets in. Mind begin to wander and the body starts to defy the mind. Safety became a main concern. And for this reason alone, the triathlon order became Swim (while the body is fresh), Bike (which involved the longest distance at speed averaging up to 40km/h) and Run (so, even if you fall/collapse, it is at a slower moving speed compared to biking).

I was a fat boy in 2010. Now? No more. Fitter. Stronger. Wishing I am racing this, again.

Now, imagine if the triathlon has the Swim part in the middle of the race, or towards the end of the race - the drowning risk will be too high. SIPE of Swim Induced Pulmonary Edema could happen even higher due to the core muscle already very flushed with blood flow, death could possibly happen and the risk will be higher. 
"OK then, we stick to swim being the "first" discipline. Can we RUN then BIKE?", one may ask.
Again, there is no specific rules about it, but it bring us back to safety. It is often easier to manage runners charging into the end of race than to manage a group of cyclists sprinting at 50km/h towards the finishing and risk crashing. Make sense?
Or how about seeing it from my perspective (and many others)...The photo opportunity at the end of a RUN is definitely better. You have time to soak in the last few hundred meter of the race - reflecting on your journey you have taken so far to be a triathlete; and in more extreme cases, the one year you put in waking up at 4am every morning to train and to finish the race as an Ultra distance triathlete - to be known as an IRONMAN. That, my friend, is only possible if we RUN to the finish line.

Drama Mama

Good enough reason for the order to be SWIM, BIKE and RUN based on Safety (and a bit of vanity)? Good, because the next consideration is the triathletes' abilities.
2. Triathletes' Abilities
Triathlon is an exciting sports. It is performed by people that aren't good with just one sports, so they need all three to compensate for their overall performances. Each triathlete has a "favourite" league. I can safely say none of them is as important as running. This is where the personal ability of each triathlete comes in. The swim course, short or long, is designed to separate the slow from the faster leaders. Opening up the lead from the start and the ability to get out from a less congested T1 (or transition 1 Swim-Bike) could possibly meant you will save a couple of minutes - and that will come into play much later in the race.

PD Tri 2012 - Swim Start. Advantage for faster swimmer to create the lead. Also less possibilities of being kick in the face.

World class triathletes have almost similar swim time. They are all out of the water within minutes from each other - adding to the excitement of the race. Those that are "weak" in their swim but strong in the bike will have their chance to catch their opponents and pass them on the Bike.

or alternatively, use it as a catch up session as you pass your friends.

Triathlon favours strong runners. The last league of the race are often very exciting as these world class and strong age groupers will often race to the finish. We have seen how close the Women Olympic Triathlon ended - with identical timing and what sets the Gold and Silver...was...well...debatable. For this reason as well, having the sequence of Swim Bike and then Run does make sense.

Taken from Yahoo!News here

You can again, argue that a photo finish on the bike will be even tighter - but you will have to tie it back to reason 1: Safety. So in the world of triathlon and after seeking the learned spirit of triathlonism, I now conclude why the sports are at such order (of sports) and why I am racing it. There is simply no reason not to do it - unless of course you are not up for the challenge to beat the worse opponent of all time. Yourself.

Swim - Bike - Run : From bottom looking up! 140.6 miles for the win!