20 or more carries a game, are pretty much gone.

There are exceptions, but most teams rotate at least two backs through for carries. Talent, injuries, etc. almost demand it. Plus, while it is probably not discussed, the career expectancy for a running back is probably the shortest of any position, certainly skill position. A back with a Sunday future wants to do enough to secure that future and, increasingly, that means limiting overall touches (carries plus receptions). I am sure coaches are aware of that, and want to protect a good player. The player would never ask to come off.

While I am sure there are counter-examples, I would guess that at 90% of the schools, the feature back probably does not account for more than 60% of the carries and those are probably at schools with a stud and little depth.

Everyone wanted to see Dexter Williams get more carries. Those had to come at Adams or Jones expense. While I didn't have a problem with Jones losing a few carries, it did limit Adams. Even managing Adams' carries carefully, he was always dinged up by midseason. If Adams had gotten the same number of carries as Denson did in three years and kept the same average, he would have broken the career record easily.