Part of the reason you don't see many young officials in the NCAA is you don't see many young officials period at any level. Quite frankly it's hard to find guys willing to put up with the kind of abuse that officials take. I know there are several officials in the local association here that would gladly stop working games but there isn't anyone capable of taking thier place.
The other part of the reason you don't see many young officials is officials organizations can be very political, and too a large degree a good old boys network. Guys that assign games have "their guys" and it can be very hard breaking into the ranks and advancing. I've been a part of several different organizations and I can tell you the Iowa City group is as good as it gets, but there are other associations and assigners in the that are difficult to break in to.
Lastly you find very few guys willing to put in the work that it takes to work up to D1 ball. You cut your teeth on youth, JH, and Sub varsity games for a few years, then you have to work your way into varsity starting with lower classes and girls contests. After a few years doing those you start getting more and more guys games, and moving up in classes. Another few years working high level HS games and you can begin to work into D3, D2, college games, and prove yourself there for 2-3 years and hope you get noticed and you begin working D1 games. So all together you are talking 10+ years to work your way up, and if you move or relocate along the way you typically have to take a step back due to the political nature of the associations and assigners.
EDIT:
I should also say this. Unless you have done the job you have no idea how difficult it is. I firmly believe that all HS head coaches should be required to officiate for one year prior to coaching. I too can sit in my easy chair and pick apart an officials game, but you have no idea how fast the action truly is when you are five feet from it. You blink, or you divert your attention for a milisecond from the play at hand and you miss an obvious travel. You know you missed it, you know it was there, but you can't call it if you don't see it... It is without a doubt the most humbling experience in my life.