No....that's not it
It's a very simple but very effective play. It's only used in one very specific situation, but if executed well it's nearly impossible to stop. I'm talking of course, about the quarterback sneak. The play the Bucs seem to have completely removed from their playbook.
Three times the Bucs tried to convert a short-yardage play, and all three times they handed the ball to Earnest Graham. All three times, they failed. That wasn't really Graham's fault, it was more that they were running into a mountain of flesh and the Bucs couldn't beat that Lions defensive line - or at least not enough to get a first down.
Yet the Bucs have the biggest starting quarterback in the NFL at 6'6", 250 lbs - only Joe Flacco really comes close. Running a successful QB sneak with Freeman should be easy, and it certainly was last year. So why are the Bucs refusing to do that, instead of relying on less successful plays in critical situations?