For me, it is very important to be in the best shape possible even for street riding. It's just more enjoyable in good shape. Perhaps this doesn't matter as much to those who can be out of shape and still be thin. For me, if I am out of shape, I am fat and that takes away from the enjoyment of riding a sportbike.
I try to run and ride a bicycle as much as possible, complimenting that with weight sessions and plenty of stretching.