They behave the way they do because they are control freaks. They want absolute control over their platform. Their ultimate vision is that they'll be the source of all your media, all your apps, etc. They'll dictate how you consume stuff. Such a setup would be, needless to say, very profitable.

As for why they can get away with it, well I'd say there are two reasons:

1) Fanboyism/zealotry. Apple has had a following for a long time of people for whom they can do no wrong more or less. A non-trivial amount of these people are in the press (Macs are big in prepress work). They just love Apple and everything they do. So when something bad comes out, they find ways to rationalize it away, or ignore it.

2) For many of the Apple buyers these days, Apple is not a technology company but a fashion company. They largely won't admit it, but they buy them as fashion accessories. They are the "cool" product to own. As such they are purchased based on that alone. Whatever restrictions/costs accompany that are ok because they want to be cool. I see the same thing these days with fixed gear bikes. They are in with college kids (I work on campus and bike to work). They buy brand new, surprisingly expensive, fixed gear bikes. This, of course, makes them harder to ride up hill, but they are ok with that because fixed gear is cool, road or mountain bikes are not.