Actually it's not just that. I believe sometimes people forget what enormous achievement it was to have _one_ centralized repo for all the apps a fragile, mobile device can have. Without AppStore, the dark ages of Symbian suddenly come into mind. And sure, Apple has had a number of flaws when it comes to AppStore policies and regulations, but part of Apple's sternness and rigidness is well justified, given the myriad of apps it has to serve, and safety and security of billions of devices that run those apps.
It's a complicated issue to be sure, but developers also benefit from a platform that has high trust among users. I think users are probably much more likely to try out new apps and even pay for them if they know ahead of time that the apps been vetted, the payment processor is secure (and already has your details), etc.
Not that there isn't crap on the iOS App Store, but I don't think it's controversial to suggest that the Good to Bad App ratio is better there than on the web as a whole.
And for some devs and some apps that’s worth giving up a 30% cut and dealing with Apple’s processes and restrictions. For some it won’t be, if they can distribute the app any other way.
