Maybe because people aren't educated about it? How do you expect someone to be an expert in something if they have no knowledge of it whatsoever. There's barely any information of how to detect what hack is what hack when doing a simply Google search.
Not only that, but PVP is changing. With every update, pvp changes. It gets harder to detect and detect the type of hacks are there are many diversions such as trying to focus on sprinting — I mean, I can honestly say that sprinting is hard on 1.7 and so I use caps lock.