Contract system that carriers impose pretty much makes everything you are saying look like nonsense.
How is this any different than Android users? The contract system with carriers isn't exactly friendly to people that want to buy a phone every month.
It's not good either way. Besides the already stated point of resale value, no one likes to buy a phone, like it, and then a month later see the exact same phone with better battery life, or a better display. No your phone doesn't stop working, but you end up regretting the purchase because you could have bought a better phone if you waited. It has nothing to do with being a slave and everything to do with not wanting to be screwed by the seller.
If you limit yourself to a contract then yes you are usually stuck with a device for 2 years. A lot of people don't concern themselves with contracts and just get whatever works. How many 4S owners on contract will get the next iPhone? More then just a handful.
If you regret a purchase because something better comes out then that's a personal issue. Something better is and always will be coming out.