Maybe because everybody know, but nobody is talking..?
There are those that don't talk and those that flat out deny it (and then call you a noob/idiot). You have to realize that no one that hacks will admit it. They knew that when they started doing it they would be questioned and therefore were all ready prepared to lie to your face. The only way they'll admit it is if they think you all ready know.
Like the BF3 hacker, most people probably start doing it because they think others are. So unfortunately, if you're an above average player and you happen to woop up on someone repeatedly, you might just spawn a hacker. I've seen this happen a few times.