Same reason why I've tried all kinds of other activities that involve the possibility of serious injury or death.
If you can't die doing it...it probably wasn't that fun in the first place.
Life is short enough, may as well push the envelope while you can.
When your time comes it comes, no use worrying about.
and finally
When you land, stop, crash and survive, surface or whatever it may be you feel a hell of a lot more alive than you did before you started.