Soccer = Run around kicking a ball into a net
Football = Throw the ball over the loving pole.
Tennis = forgetin' get the ball past the opponent.
Baseball = Hit a ball and run in a triangle-type thing.
Mmhmm, see your point.
Note that all of yours include competing against opponents.
The aim of those games is to show you're better than the opponents.
Where as with Parkour, it's just for yourself, really.
Besides, if you guys are jumping around places and hurt yourself, you'll have yourself to blame, yet I'm sure atleast a few people would dare to press charges on the owners of the property they were using.
That, or they end up breaking other peoples property and, that's unfair to damage someones property and not pay for it, just because you wanted to run down sidepassages and jump off walls instead of take a proper route.
It's fair that it's made illegal, because otherwise there will eventually be someone having to pay money for something that they shouldn't need too, or someones going to get hurt.