For me it is the most effective form of transport for many things like going to work and buying groceries.
As I am pretty much only an urban rider, I never have an issue with parking anywhere, which had become quite problematic for me with my car.
Also I have saved a small fortune by being "Car Free" for the last two or so years.
When it comes to exercise, the exercise is a bonus only, as I prefer other activities to cycling to get an exercise fix.