1. Football is way bigger sacrifice than people realize. If you are putting in thousands of hours and not playing, why not make a change for the opportunity to do so?
2. Depending on conference... four years of scholarship are not guaranteed. If you aren't getting play time, there is no guarantee that you won't be moved off the roster. Why not go somewhere where you can contribute on your terms? No loyalty
3. If you are a walk-on... this one is a no brainer. You are putting in thousands of hours, taking time away from academics, and paying the university for the privilege to do so. The path to a scholarship is going to require getting practice and game reps or transfering to a school that needs your skills more. (The "Jordan Stout" scenario)
4. If your ultimate goal is to play on Sundays... that's not going to happen without game film. Better to play at a smaller/lesser program than have limited opportunity/exposure at the larger program. (The "Tavien Feaster" scenario)