+1 to this. I did Heathrow to Bermondsey for £110 (first time in London). Then next morning, found myself wondering why I didn't just use the train. On the way out, I did use the train, and lets just say, I still think about that £110.

I've only traveled in Europe and Asia so far but this never looked like an issue to me.

Also I'd also use the transit system for the following days in the city, so have to learn about it anyways. (Not that there's really anything to learn)

Lugging around luggage through buses and transit, especially if there are stairs involved, is not pleasant.

It’s not pleasant in cities with great transit like Tokyo or Seoul, and it’s downright miserable in most of the cities being discussed here in this thread.