This is actually a theft deterrent. Bus drivers can't get at the money to give change, so they can't be held up either.
> Probably that's why people look at you very suspiciously when you approach them on the street to ask for a direction.
That's part of it, but Americans are deeply distrustful of strangers. It probably plays along the same lines as our finding suburbs safer than inner cities.
> Tipping baseline is very high. Although I'm a capitalist, I consider this practice to have nothing to do with capitalism.
It's strictly a cultural thing. I'm given to understand that in Hawai'i tipping used to be considered insulting, and perhaps that's still the case in places (I've never been). Also, in different parts of the country tips are compulsory for different occupations. In the Southwest, restaurant service is about the only thing you tip for. In New England it's a different story.