It's not known if Maps was removed because of Apple or Google or both. So while there's no choice on having Google's Maps removed in iOS 6, the reason it happend isn't clear. When it came time to renew the contract one or both parties could have made unacceptable demands, leading to the current situation.
Yes, it's interesting how everyone has been assuming Apple booted Google off of iOS as an act of vindictive retribution. Everybody assumed that Apple's maps would have magical qualities that would leave Google looking second rate. Now that it seems to be the other way around you have to wonder if it was actually Google that pressed the big red button on the maps contract.
I think it's not really a case of who booted who off. I assume that Google wouldn't let Apple have any of the good features like vector maps or turn-by-turn navigation. Google Maps on iOS was already the shittiest mapping app across all platforms. So Apple have replaced it with an even worse alternative but at least it has some headroom to improve vs 2004 Google maps experience which was never going to get any new features.
I think Apple made the right move. Even if Google is 10 years ahead in mapping, the experience you got on the iPhone was Google maps from 2004. So Apple is only 2 years behind 'iOS 5 Google Maps' and given the resources they have to throw at the problem it'll probably improve quicker than that.