They are probably the most overlooked, ignored, and disrespected guys in the NFL.
Many fans even judge DT's or NT's by how many tackles and even sacks they have. They don't understand that this position has an effect on every other position on defense. They stop runs at the line of scrimmage. They close the hole to runs in the middle of the field. Sometimes their job is simply to get in the way.
Physically, they cause the RB to deviate from his intended direction which allows the LB's to come in and get the stats. Some of the best run stuffers in Dallas Cowboys history were almost all top 5 overall picks in their draft like Bob Lilly, Randy White, Russell Maryland, and Tony Casilles, An excellent run stopper from the DE position was "Too Tall Jones", the #1 overall pick in the 1974 draft.
Every Cowboys Super Bowl team had at least one of those guys. It was also the reason the Cowboys were ranked #1 against the run for many of the seasons they went to a Super Bowl.