It wasn’t a guarantee, but they strongly implied it.
When I was a kid, there were public service announcements - one of them had the tagline of “you ain’t going nowhere without that sheepskin.” I don’t know if it was the government or the colleges that were behind it.
What are you going to require every car salesman who told a young guy he was going to really turn heads and get the attention of young women once he bought a new car to somehow reimburse the buyer, too?
Free advice is all over the place. Doesn’t mean it is all good or that it should all be listened to. And college was a good move for millions of Americans.