Yes, this sort of thing is discouraged - but my point is that anyone who wanted to learn what is being taught in CALC 405, or what-have-you can currently do so, under the table, for essentially free.
My argument was a mild push-back, pointing out that it's more difficult in some respects (e.g., you might not have access to some of your preferred professors), and that it _does_ actually happen occasionally.
Do you have any insight into why more people don't take advantage of that opportunity? Anecdotally, before I attended university I didn't value a college education beyond the slip of paper at the end, and even if I had wanted just the education without the degree I wouldn't have known that I could just sit in on my classes.
Because they correctly value the learning to be worth ~$X,000, but the accreditation to be worth ~$YZ,000.
When you put things that way, the 20-40 hours/week of time that goes into getting an education becomes a lot less of a good investment, if the only payoff is that you get to learn.
As long as "learning in person" includes one-on-one time with your professors and access to a university library I agree with you 100%.
> without paying a cent
It's pretty easy to get into hot water with the university if you have any legal ties to them (e.g. by having been a student). It's common to require some fraction of ordinary tuition to sit in on classes.
> Nobody takes attendance, and if you look like a student, nobody's going to notice that you're not actually enrolled in the class.
Enough people do take attendance, or at least take a look at the roster ahead of time (in smaller classes). I had a better success rate speaking with the professor ahead of time and asking if they minded. It's also worth mentioning that not all professors are willing to put in extra one-on-one time with an unofficial student.
> nobody actually does this
Admittedly the slip of paper at the end was important to me, but I saved a little money taking some of the classes I wanted unofficially, and I wasn't the only person in my university peer group to do so. It was also a nice way to sidestep some bureaucratic prerequisite issues for classes outside my major.