Isn't most of it arbitrary?
There are a couple of basic human physical behaviors that demand competition - running, swimming, jumping. 100,000 years ago some guy looked at some other guy and said, "I bet you I can run to that tree faster than you."
But beyond those basic motions, the rest is just arbitrary.
For example, what's with the hindered swimming? Swimming as fast as you can for distances X, Y, and Z makes sense. But who came up with swimming backwards? Or hopping in and out of the water in a big flopping motion? Why don't we have running races where people run backwards? Or hop up the track? Or cartwheel?
Does anybody really care which person spent the last 10 years perfecting the flopping in and out of the water with arms flying wildly around for a distance of 100 meters? Would a one-legged hop race up stairs be any more sensible?
The triple jump? What's that? Three big steps before a leap? Why three? Why not 2 or 4?
Gymnastics is the worst. After floor, the rest is just silliness dreamed up by somebody some time ago. Flop around on a high bar? On rings? Jump over a horsey thing? Flipping around on a 4 inch wide beam? What's the point?
The decathlon? Makes a bit of sense. Chuck a spear, run, throw a rock, throw a rock on a rope, run some more - is there swimming? Throw in dragging a woman around by the hair and you've got nature's basic - who's the best cave man competition.
It's great to do something you love. If you love synchronized diving, more power to you for being able to win a "gold" medal for it (worth about 500 bucks because mostly not gold, despite being twice the size of Beijing metals).
Who am I to say that it's a waste of a person's youth to learn how to flop around on matt or throw a spear or run or play basketball? Do what you love, and if you can paid endorsements to do it, great.
And Phelps - smoking weed is fun, but it makes accumulation of gold trickier.