Because your meant to do them in accordance with your down 1, not raw. That way you buffer grab into down 1 making it excellent for tick throws. Of course this only works if they block, if they get hit with the down 1 then grab will just whiff
But if that happens then you know your opponent is mashing and u can just go for the counter hit. Also it helps if you wanna end combos with it since down 1 into command grab works at every height. Works way better that trying 2 land raw grabs after a launch