My everyday use case for navigation is along the lines of having a buddy tell me to avoid a certain route, due to traffic.
I've tried Google Maps and Waze (as well as Google's dashboard thing which keeps a semi-permanent time estimate pinned to some area on your phone), but these all miss the main point in my use case - I only need an detour away from my daily commute maybe twice a month. On the rest of the days, I know how to drive home, thanks. This is not enough for me to be semi-permanently firing up heavy apps to check the route. A simple thing which says "hey, I've noticed you just got in your car, and you're probably heading home - don't take highway X" would be nearly perfect.