I know that in terms of financial aid in 25 years old is when your Parents income is no longer accounted for in your application for financial aid. For some students 25 years old is when they would be able to get a Pell grant because they are no longer counting their parents income. Since the federal pell grant covers a large cost of community college for many students it’s probably part of how they will cover the cost and why the age limit is 25.