Not banning them as such but it certainly sucks when timewasting is used as a deliberate tactic. If players can get a time violation for bouncing the ball 987 times before serving then so should a bathroom break whether they are really taking a leak or a sh!t.
The problem is that (top!) players barely ever get a time violation code for whatever a time wasting trick they try out. Umpires don't do anything against excessive ball bouncing or other time wasting tactics either.
I agree... it's bad. But that's what you get if rules aren't being enforced.