You're just taking the Western code of social conduct as "normal". Human interaction is completely normal and natural.

Isolating yourself in certain situations isn't the same as not having human interaction and sticking 10 million humans in a small area and expecting them to always interact with all of the others is in no way normal or natural. Sometimes interacting with ~100ish people (within an order of magnitude) over your month is natural. Too many is both exhausting and diluting of the meaning, too few is lonely and over isolating.

You're trying to follow an out-of-date map. Our technology-infused growth of the past 50 years has produced more widespread mental illness and psycopathy than someone in the 80's could have even imagined. At this point in our societal evolution, you cannot assume that HUMANS THEMSELVES are either normal or natural.

Human interaction, sure. Human interaction with complete strangers, 10 inches away from you, enclosed in a metal tube you cannot escape from easily... not so much.