Much has been written lately about Apple abandoning Google maps in favor of their own in iOS 6. There are, it seems to me, two aspects to the change and the imbroglio that followed.
The first is why Apple decided to make the change at this time, especially given that their contract with Google has still had a year to go. I, of course, am not privy to Apple's thinking on this but John Gruber of Daring Fireball, who follows Apple closely, does have some insight into that thinking. He's written two particularly good articles that examine the issue. They're good reading and informative so I recommend you take a look if you're interested in the timing angle.
The other aspect is why, once Apple did change, their application performed so poorly. Certainly, Apple knows how to write software and they've bought lots of talent in the mapping arena so the problem must lie not with the software but with the data. At first glance it's hard to see how this could be. After all, Apple bought all those mapping companies and got data from TomTom and Open Street Map. What could be so hard?
An article in The Atlantic helps explain how huge and difficult the problem is. The article is very revealing and gives a sense of how labor intensive producing world class maps is. To gain an appreciation for the magnitude of the effort, consider that WebProNews reports that Google has 7,100 people working on maps. That includes 1,100 full time employees and 6,000 contractors.
The takeaway is Apple has a lot of work to do to raise the quality of their maps to that of Google's. Given the famous Apple focus, it's just a matter of time until that happens. In the mean time, of course, Apple maps will be inferior. While you're waiting, go on over to the Atlantic and read the article. It's very interesting even if you have no interest in Apple's map problems.