I'm a one man shop that does App development as a hobby while simultaneously maintaining a full time job. Having someone handle 24/7 hosting and billing and a sort of rudimentary QA on the final product (so the users will trust it better) is something of value. In many cases, costs and time would be prohibitive for a new, small shop to do all these things itself. So they do something for that 30% other than rubber stamp it.
Also, $99 is a pittance - how much do dev kits from Nintendo, Sony and Microsoft cost?
Now another poster pointing out that the rules are different for larger companies that develop on Apple's platform - yes they are. I see competing apps that violate the backgrounding policies (for good reasons) that I could never get away with if I tried.
One example is playing silent audio while streaming via DLNA from the iOS device to prevent the OS from putting the app to sleep after 10 minutes or so. A big company just does it and has done it for years without consequence. Another small developer in my niche needed to do this as well, but was forced by Apple to remove it unless there was a specific function for it. So the developer instead added a useless "visualizer" that made graphic effects to music picked up by the microphone which is then put in the background and hidden - just to get around the rules. I have not added DLNA streaming yet because of these headaches.