Additionally this might be important for shutting down blacks pressure on the a2 square. Black has a threat of b4, cxb4, Nxb4: whites knight on c3 is the only thing stopping Qa2 for now. If black can sacrifice for it or deflect it then there is a threat on a2. It wouldn't be checkmate as the king can escape though.
Ponziani
Thanks for your reply. It is difficult to account for move order and transpositions but i feel like i see the slav response about 50% of the time. Until i study it more, im often opting to exchange the central pawns and then just develop my pieces as white. Unlike in other pawn exchange openings like the French exchange or Caro kann exchange, i feel like for whatever reason it doesnt dry out too badly. If i stopped playing the Nimzo Indian i feel like i would opt for the slav but only after closing the pawn structure after getting my bishop out. Because i don't play this as black, I'm not sure if I'd try to hang onto that bishop once its out and prone to attack or try to keep it in the game, i don't think its worth the time trying to make space for it to retreat. Meanwhile when i used to play QGD it felt too cramped and i never felt like i had the tempi to devote to trying to fianchetto the light square bishop.
Ah yeah the rook move refutes this