The only routines using floats are for bezier curves, right? I think the author actually tried to show the universality of the principles, and routines are seemingly similar enough to back this premise up. It will be of course possible to avoid floats in them, which may or may not simplify the routines, but I guess such changes can destroy the inherent similarity and the author was not brave to try that out. (Multiplications are more common but the same argument applies.)