It's very hard for people to learn by interacting with other people directly. Two major reasons:
- Interaction triggers people to behave and interpret socially. They put most of their effort into social hierarchy stuff instead of learning.
- People are complex and flawed. It's a lot to deal with in addition to the subject itself (the subject is e.g. philosophy or physics concepts). People have to deal with miscommunication, scheduling, mutual benefit, different background knowledge, being able to think about other points of view, etc.