Or just practice blocking more -- single blocks, combo blocks, RB screens -- all of these work through as many (although different) angles as a TGU hits, and with a lot more force and the complication of non-stationary feet.
And the TGU is a somewhat complicated lift that most aren't familiar with -- any time spent in the gym is time not spent practicing. Is time spent learning this new lift really going to make my player a better performer than just practicing more? It's not an easy sell to the offensive /defensive coordinator or head coach....and they're the ones who determine how much time is given to S&C....
In Division 1 football, NCAA rules specify the athletes can spend no more than 20 hours a week on athletic activities. ~70-80% of that will be field practice and drills, 5-10% on play reviews and white board time, and 10-15%, max 20% on S&C. So you've got 2-4 hours per week (it will go up and down) for all the S&C, which also has to include any sprints, sled work, agility ladders, and the like, as well as any actual weight room work. That's not a lot of time to learn a new, complex lift like the TGU.
As a center, one of my main jobs was to block / neutralize the nose tackle.
And nose tackles are crazy and big SOBs...nose tackle is usually considered to be the most physically demanding position in grid iron football.
They were usually 50+ lbs heavier than me.
A nose tackle with 300+ lb bodyweight on you generates a lot more force on your body than a typical TGU.