1. Consider how many drives stall as a result of holding penalties. I don't know what the precise percentage is of drives in the NFL that stall in which an offense has committed a holding penalty, but I'm guessing it's at least 50%; probably a good bit more. That 10-yard setback is tough on an average offense, let alone a bad one like the Jaguars'.
2. Consider that Gabbert averages 10.1 yards per completion. So when a receiver drops a pass, the Jaguars are set back 10.1 yards on average from where they would be and should be otherwise. Plus the Jaguars lose a down and, on average, a first down is foregone. Dropped passes, therefore, on average are far more damaging to an offense than a holding call.
3. Consider that the Jaguars average -- what? -- 5 drops per game? That's equivalent to 5 offensive penalties per game that are more damaging than an offensive holding penalty. Drives are difficult to sustain with holding calls, and even harder with drops. Gabbert just can't be blamed for this offense given what he's working with.