Maybe he came down with something and was told to stay behind, lest everyone else also get sick?
Sometimes it may just be the simple reason.
There is a limit on SEC away games on travel squad. Most teams take 3 QBs, as they need to take who will play and contribute in some way (Offense/Defense/Special teams). Morris is #3 so that they can RS Barnett. If Coker and Bateman went down, I would bet it would be Barnett as the guy if still in playoff picture--Like AJ was McElroy's backup. Morris is a signal caller, Backup punter, Backup QB, and probably the backup Holder and who knows what else he can play--so he will always travel
Coker Starter
Bateman #2, Holder
Morris #3/4, Signal caller, Backup Punter, Backup Holder, Water Boy, Manager etc. LOL
Barnett #3/4 Emergency Backup/Scout team
Cornwell #5 Scout team/Dresses for home games