To begin with, can anyone name the last college head coach, with zero experience in the NFL, went directly to the NFL as a head coach and had success?
The last one, and just about the only one I can think of, is Jimmy Johnson and that happened more than 35 years ago.
Freeman may eventually do it but he is smart enough to know that it isn't a path to success. Good coaches with large egos thought they could do it and flopped. And he is likely to earn more as a college head coach than a pro one unless he has high levels of success in the pros.
Based on watching Freeman in action, his personal style works better at the college level than the pro level.