While I don't appreciate how much Apple is trying to close off the system and make it a black box, I don't think a free-for-all approach will be any better. There will be so much junk to sift through to find something good. Not to mention malicious app possibilities.
There's a big difference between monopolising and preventing harm.
How'd you feel if Starbucks refused to sell coffee without sugar in it? (wouldn't be suprised if the Sugar Lobby hadn't already thought of that one lol)