Prior to 1993 (this is the date the rule was changed in the NFL, not sure if NCAA changed the same year or a few years later), if a QB was under duress and threw the ball where there were no receivers in the area, IT WAS INTENTIONAL GROUNDING. Obviously this was a judgement call but so are a lot of other penalties (holding, pass interference, etc.)
The obvious reason was to allow the defense to get the benefits of a great play.
Then, the NFL decided it was an offensive league (pun probably intended), and put in the new rule that the QB can just throw the ball away as long as they are outside the tackle box and get it past the line of scrimmage.
This rule has ruined college football.
When the defense makes a mistake, there is no rule that allows them to recover. But, now when the defense makes a great play, it is often completely negated. Instead of a 10-15 yard loss, we just forget about it and bring it back to LOS.
In Saturday's game, Pryor messed up and failed to get the ball back to the LOS. So, penalty called and a great play by the D was maintained. The D then forced a punt. Imagine on that drive what might have occurred if Pryor had merely gotten the ball past the LOS. Second and 10 not second at 24!
I hate this rule!!