Plus if you're bringing the block every time in games that means you'd be bringing the block every time in practice. One would think the players would get slightly better than the average player in learning all of the intricacies in avoiding a roughing the kicker penalty. In simple terms, the 5 rushers should get very, very good at not running into the punter.
And the whole, "Running into the punter" is such a ****** pessimistic view point too. Outside of probably blocking more punts in which the opponent executed the snap exchange fairly well.... What about a high snap that causes the punter to take that extra second? What about the bobbled snap that causes the punter to take an extra second? What about drop snaps and snaps over their head? Bringing the block every single time turns these sorts of things into huge plays where as not bringing the block might turn these plays into nothing.