Why does everyone defend the unions so much here? They are the reason we have a sub-par education system in the US. Teachers get automatic raises not based on

Why does everyone defend the unions so much here? They are the reason we have a sub-par education system in the US. Teachers get automatic raises not based on merit and it's very difficult to fire a bad teacher. Until this problem is fixed (which the unions likely won't fix on their own), the other things you try aren't really going to help.