Apple has every incentive to make the release polished and refined. Apple's profits come from hardware, and so they have every incentive to keep me, the customer happy so that I will continue to shop from them. Yes, their profits come from hardware, but when I pay that price, it comes with the expectation of continued and timely software support, an integrated computing solution which just works right out of the box, and a seamless and hassle-free user experience.
Software can never be 100% bug-free. If you are trying to insinuate that Apple is acting the way out of complacency and laziness, then you could not be more wrong. Apple does care about the end user experience, and from what I can see, Apple is working very hard to ship the best products they can, given the constraints and challenges that they face on their own end.
Apple is not slacking, at most, they probably have a bit too much on their plate at the moment. If they don't act on an issue right away, it's likely more because they are stretched thin. They will eventually get down to it, just maybe not right away because there will always be a more pressing matter to see to at the current moment.
The best answer I can give you is "iOS 7 was a bitter pill that we all needed to take." I know it sounds apologetic, but iOS 6 probably felt polished only because it brought the fewest new features to bear. I remember sitting through the WWDC keynote and the insufferably arrogant Scott Forstall and thinking "That's it?" to myself at the end of the whole thing. Maps sucked and the more memorable features were probably do-not-disturb, panorama and 3g-facetime? It was stale and brought practically nothing to the table and I will forever think of 2012 as Apple's lost year.
Basically, I still don't see how making updates paid will improve its quality. It's still the same software regardless of whether 1 person downloads it or a million people do. Apple is not going to magically start working harder than is humanly possible just because they stand to earn a few extra million dollars from it (which is really chump change compared to the profits from hardware).
Your stance seems to be "If fewer people download it, that's fewer people making a bad choice", which solves the wrong problem. I don't have a perfect answer to this, but I do know one thing - that answer that you are proposing is wrong.