Because when it was introduced in wow, it exposed me to so much absoloutely disgusting human refuse, i stopped using it to group with.
Now, if it was just server specific that might be ok. At least if it's your own server, eventually there gets to be more of a community feel, people get known and it's harder for the less than pleasent types to practice their craft...
Then the problem isn't the tool but there needing to be a way to punish these players, which btw I've never seen in WoW using that tool. If people are having bad experiences then why not just have a rating system so people get shamed if they constantly do this?
It is a simple thing to sort out.