Because this takes a lot of time to do and most of the consumer base would bitch and complain that the art department spent their entire development cycle just scanning players. This instead of working on new animations, maybe adding parts to a new halftime/postgame show, etc. Also not all of these players have the time to get face scanned. They are working 8-9 months out of the year depending on playoffs then they will want to go onto vacations and spend time with their families.