Assuming the denial is actually enforced, which it normally is not. And generally speaking the only enforcement mechanism is for somebody with standing to bring a lawsuit.

GPL V2 licenses are violated on a constant basis in my personal experience. (I used to run a business that competed in the MySQL market.) It is relatively difficult to detect inclusion of GPL code in shipped binaries, for example, especially if the audience of users is not large or the binaries are part of a larger system.