So, why doesn't everybody get to decide for themselves? It's pretty obvious that opinions differ, so people should be able to modify some simple setting on where their preferences lie in this respect. "locked down", "open for selected classes of apps", "open" or something like that.
For me, "locked down" is a choice I make when I buy an iOS device. It's not something I look for in servers or desktops, but in tablets and phones it is very much something I appreciate. Many people have other philosophies from mine: fortunately, so do many other computer vendors.
Apple doesn't blindly extend trust to app vendors - neither do I, particularly. Apple doesn't trust most folks to decide whether to trust an app vendor - neither do I, particularly.
