Well, I am going to list out a few things for you.
1. The learning curve
This is one of the largest reasons. Toribash is very hard understanding at the begining especially when
you think about how many Smurfs are in beginner lobbies.
2. Tc
Tc is very hard to earn for the most part unless you do ranked. (which most beginners don't bother with).
Those are really the only things I can think of.