So on 2nd and short, they're selling out to prevent the big play (some teams view 2nd and short as the ideal opportunity to take a shot downfield) and don't really care about giving up the 1st because they'd rather put the opponent in a position where they're likely to make a mistake. I think it's a silly and morale-killing philosophy, but that's the reason they play so far off the LOS on 2nd and short.