Also, from a professor's viewpoint: not everyone is ready to work hard enough to succeed at college straight out of high school, and yet, in over 20 years of teaching, I've never seen an older student coming back to school from the workplace (or, more often, combining the two) who had this problem. They have other issues - sick children, schedule conflicts, etc - but motivation is not a problem for them, because they are there by choice, not default.
And, on a sadder note for everyone involved, not everyone is intellectually capable of college-level study. It's heartbreaking to watch someone work their tail off and just. not. get. there. over and over again.