It really does make way more sense with a RB. I mean, it's not like other teams don't know what's coming when the Eagles line up like that. So it wouldn't matter if you gave it away by swapping your QB out with a big fullback or something.
Still have to have guys in the line that can move forward a little bit. Texans usually get no movement forward.
If you put the ball inside his helmet, he just has to literally lean a little bit. That's a neck joke.
According to reddit, the answer is because it's harder to take a snap under center than it looks. QBs are used to doing it, RBs doing it may risk a fumble. The second reason why teams don't use RBs is because with a QB there is still the threat of a pass even if it's minimal.
I would add a couple of players the should specialize in the tush push, get a big QB or RB and use a guy like Desmond Watson to push say Mixon or a TE that's playing QB. You wiil gain 2-3 yds most times.
