27? 28? 35?
Let's face it, even IF you attempt to graduate in 3 years, most people will not be able to, so you start college at like age 27 and fail several exams due to sadistic profs/your IQ not being high enough.

Then there is the point that lots of those older students are former neets, so really, even if they manage to graduate in, let's say, engineering, what job market can they expect realistically?