Because I don't need to, and there are no advantages to me doing so. Taming is also the most difficult skill to raise, so it should be obvious that if I am going to put 15 skill points on a jewel, taming would be the one to do that with. The only possible reason for me to take my taming to 120 would be if I felt I had something to prove, which I don't.
However, some day I would like to solo Dread Horn, and I'm working on that 800k zoo point title, so it's not like I don't have goals in game, it's just that 120 taming isn't one of them. It also doesn't mean I don't recognize the achievement either, which is why I am always ready to congratulate someone whose character becomes a legendary tamer.
