If they were to let GM's take actions against these bots, they would drastically limit their numbers. These lvl 70 gathering bots are no way close in number to the RMT or leveling bots. And you can even tell by the fact that people on each server already know these botters. And if GM's were to take one down, it would cost the botter a lot of time and/or money to make another one (depends if they bought a level boost or botted their way up to 70). And within a short time of doing so, the GMs would only have to deal with a very limited number of gathering bots, instead of the mess that we have now.