At the next level, other than 1 or 2 each draft, RBs don't get paid anything like they used to. The game today is such that very few premier backs bring near the value they once did. Teams get greater value from two 3rd & 4th rounders than a single 1st round pick.
It's also a short-lived position. They look at it now like a pitch count: you can only take so many hits in a career. Playing in the SEC takes a heavier toll than most conferences.
So if a junior RB understands the passing game, runs good routes out of the backfield, can move into a receiver's position effectively, and understands the complexities of pass blocking... he really needs to go get paid while he can.
It's an individual decision, but Alvin's extra year in college would have to be worth (to him) at least a season of being paid to play. Once the university has prepared a young man to go make a living, we need to thank him and encourage him to go begin his career. That's another aspect of being a VFL.