I have thought the same thing myself. I think running up the middle and being stopped cold accounts for probably, at least, 50 percent of the effort. You would think they would learn. I watched a high school football games last fall, and it was absolutely amazing.
Not to mention the punt return, where the receiver will invariably run toward the largest concentration of opposing players.
Short yardage plays rely on timing. If the front line can produce a gap and the running back can hit it in time you typically gain 3 to 4 yards. No gap and the play likely gives you a 1 yard loss. so on a percentage basis you gain 2 yards per play.
Now the truly great running backs can tell if the gap will be there and have the peripheral vision to see other openings. They can make a spit second decision and many times capitalize. I have to believe in this era of statistics and computer models this type of running back is discouraged by the coaching staff. It may also be that too much ad libbing encourages other players to try it that don't have the talent to pull it off.
The Babylon bee again hits to close to reality