Honestly, I think that Apple should just have stuck with google maps. It would have made all of our lives so much easier.
What if Apple didn't have the option to continue using Google Maps? I know if I made a phone and had a great mapping service I was using to sell that phone, and was currently licensing that mapping solution to my competitor, when the contract was up I'd make it as uncomfortable (expensive, lots of restrictions, etc) for them to use/relicense as possible.
It could also be that Apple really wanted to get into mapping, I suspect that there is a lot of potential revenue that can be earned and technologies that could be implemented if you controlled the mapping infrastructure. I will say however, that if I were Apple I would have released an open beta with iOS 5, and then replaced Google Maps in iOS 6, but perhaps they were slow to move and it just wasn't in the cards.
Fortunately, it seems that in my particular part of the world Apple Maps seems to be accurate - even the satellite imagery which I wasn't expecting to be at all quality or recent is only from a few months ago. So I was pleasantly surprised by that.