The difference is at a university you have to learn ~5 different subjects at once. On the job you only learn one. It's more of a "Breadth first" approach.
What you learn on the job is largely up to you. You can choose to focus narrowly on your job and learn nothing more. Or you can stick your fingers in more pies to learn much more.
When I was in school mostly the poor kids and lower middle class had jobs, but I wonder if that's still the case.