Hi,
This is Robin from Kurviger, I just got pointed to this thread.
As noted before, the fastest route option of Kurviger is not intended as a competition to Google maps or similar offers that work with live traffic data. I also use Google Maps myself if I have to get to a destination as fast as possible. If I want a nice ride (even with a car), I choose Kurviger.
The intention of the fastest route is to have a mode to travel to your riding destination fast, but still providing some fun. Usually Kurviger drives of the highway if the detour is a nice ride. I think no one enjoys riding on the motorway for hours or through cities, especially if a slightly longer detour would be heaps more fun.
Cheers,
Robin