So why should CFB players be held to a different standard? If they have enough talent to play pro football, what does being in college do for them. If that is their goal in life, then they should be able to pursue it as soon as possible.
It probably has something to do with the fact that most 18 year olds are not physically ready to play against 22+ year old grown men. More than any other sport, due to the inherent violent and physical nature of the game, it probably is one of the toughest transitions for an 18 year old versus a 20-21 year old would have.
Those couple years developing in college are key. Of course you always have an outlier like Jadavon Clowny who are physically mature and beast since 18 so there is always going to be exceptions to the rule. I am really not sure what the correct answer is to the question, just pointing out why football is a different game than basketball and baseball.