Yeah, plus traditionally sacks are an unexpected bonus for DTs. You want them to generate push, clog the middle, and maybe apply some pressure, but no one really expects a ton of sacks regularly from the DT position. Pass rushes dependent on DTs are unlikely to be super successful unless you also have good enough ends to seal the edge. After all, a charging DT leaves a hole in the middle and if the ends can't contain then there's a vulnerability there too.
Mind you, this understanding of pass rush may be entirely obsolete. Frankly, it seems that the four man rush even with good DTs and DEs is obsolete for the most part, too. At least it sure seemed that way under Rivera.