It's a strategy.
The idea is that over the course of a year you are more likely to have things go bad than go well on a punt return (fumbles, injuries, muffed punt, running into kicker, clipping penalty, fake punt), so that you go into safe mode on the opponents punt - - lightly rush (to keep them honest) and fair catch. If you need too much to catch the punt, just let it bounce (like don't make running fair catches).
There is also the idea that in the college game, the guy who might be your most sure-handed might not be your most dynamic with the ball in their hands.
I'm not saying I agree with it but that's the theory. I'm pretty agnostic to it. For example, we returned 15 punts all of last season. Ohio State returned 20 and Alabama (in two more games) only returned 19.