This may sound odd, but until that very day, I hadn't realized why there were such things as universities. I'd thought it was just rent-seekers who'd gotten a lock on the credentialing system. Why would you need teachers to learn? That was what books were for.

It's not clear why it isn't true as originally intended. Books are enough for understanding anything, you'd just need good from-the-ground-up textbooks and probably months or years to read them. Teachers are out of this loop, and from personal experience I see teacher-mediated learning as inefficient, given motivated student and availability of good textbooks.

Universities institutionalize the very process of learning, which helps if motivation is weak and goal is not even on horizon, and as a result universities supply bigger amount of trained people than would be possible by just printing good textbooks.