To add to what others have commented about this, I think if there was a true Coach Mode on NCAA that many AD Moders would use that option as often as they would 'watch' a game.
Many people think text sims take care of the segment of the market who crave true 'dynasty' modes: recruiting; depth charts; administration of the program; etc. But, the real payoff for those gamers is watching the game unfold play by play. SO much time is put into graphical presentation that it is a waste not to enjoy it. A text sim option is a poor substitute. That is why those games are niche.
Personally, I don't see much difference in watching a CPUvCPU game and watching a televised Pro football game or a movie, or even playing a simulation game (Sim City, etc.). People choose to be fans of pro football teams for whatever reason, but no one has any real vested interest in the outcome (wagers notwithstanding), much less an effect on any plays, yet you sit there and watch and get excited about what happens. Same with movies, most of which are even predictable.
In a videogame, you set a lineup, depth chart, and all these other administrative tasks, and all these tasks have some effect on the game. We want to watch that play out, enjoy the suspense, enjoy the payoff. Would you like movies if you only got to see a couple of sentences of text summarizing what happened?
If you like to control every aspect of your game, great. But I can get so good with a controller that it really doesn't matter if I recruit well, or call the right plays, I win anyway. Coach Mode or CPU v CPU is much more strategic, a much more realistic challenge. That is why many try it, and most who try it stick with it.