I second aeh. For certain subjects such as math, it is very hard to learn new things as deeply as you need after 25.
I also think delaying college means delaying being fully independent in life, that has many implications regarding marriage, and kids, etc.
The actual number of people who finish their college degree after the standard 18-22 age of years window is very low.
I think the root of the problem that the college professors are facing is K-12 education--students of cuddled too much in high school and they are not prepared. And some people maybe should not be in a four year college anyway, maybe.
