Those kind of guys make coaches nervous. FB coaches feel comfortable when they are in total control. The players have to do exactly what the coaches draw up.
This is why Tim Tebow couldn’t keep an NFL job even though he kept winning that season in Denver. No NFL coach was going to risk his livelihood on a player freelancing. I know a guy who played in Denver’s offense with Tim that year. He told me nobody (including the other 10 Broncos on the field) knew what Tebow was going to do after the ball was snapped. That was just too much risk and freaked out the coaches.