From the post:
Some of you are wondering why we are developing separate location based apps. In our user tests we realized that people want an easy and fast way to solve their every day needs like walking, driving or riding the bus. With our apps and the power of Windows Phone you can for instance easily pin to start the destinations you go to more often or the apps that really matter to you. Also, we can develop much faster new features if we keep some apps separate.
Not mentioned in the post is that Nokia have rolled this suite into a single app previously. A number of versions of Nokia Maps on Symbian OS had everything rolled under the single icon, but as the geo-location platform involved, the functionality was split up through shortcuts on the home screen, and then as separate applications, driven by user feedback.
While we might not have seen the combined solution on Windows Phone, Nokia have experience, and feel that the unbundled solution is more flexible.
Read the full post at Conversations.