This is why kids can't have nice things.
Kids should not be allowed to have toys until they are old enough to have to rebel against their own adult-hood to get them.
To be fair, some figures do say "adult collector" on them. I wouldn't give those to a kid, mainly because they arent designed to put up with the rough handling a kid tends to put toys through.I have no objection to kids having action figures, it's really just a question of durability, and a kid getting disappointed when Batman's arm breaks at the elbow 20 minutes after buying him.
The thing that always got me was: if you want a 3D representation of a superhero that's too delicate for much play and is designed to sit on a shelf, why not get a figurine? Lot less awkward-looking than a toy too, with those ball joints and hinges all over the place.
price point? posability? nostalgia for when you DID play with toys? just a few ideas.
The same reason people buy older muscle cars, the cruise around at 20 mph (15 if I'm behind them and in a hurry). The potential for more than the careful use you give it is part of its charm.