Part of the reason for that is also because a high percentage of elite talent gets taken straight out of high school and never sees college. So unlike football or basketball, a majority of the best 19-20 year olds in the sport are not in the NCAA. Especially if you factor in international signings, which football has almost none of and basketball considerably less.

But if you just look at the list of All-Americas every year:

http://en.wikipedia.org/wiki/College_Baseball_All-America_Team

The number of guys that you'll never hear from in a professional baseball context is really high.