Brazilian cities are quite densely populated. There are around 13,000 people per square mile in Rio de Janeiro, for example. (I know Americans automatically attempt to put things in a USA context but trust me there is no comparison).
The effect is that everywhere you go in the city, you find yourself subsumed into a mass of people. It is literally impossible to walk down a street unimpeded by others. Urban Brazilians, thus, accept a kind of rule of road where you can touch other people without incident. Basically, if you need to pass another person, you touch them on one side and they will move slightly to the other. And, if time does not permit, you can just brush past another without controversy.
This acceptance of touching is quite the opposite of American culture where the slight brush of another, especially of the other sex, can lead to legal charges!
I have heard many American men speak of their increased confidence with women upon returning from Brazil, and undoubtedly, I believe the closeness of the people in Brazil plays a role here. These men, some of whom experience little daily physical contact with attractive women, suddenly find themselves literally forced into touching, brushing up against, and standing face-to-face with women incessantly.
American women have expressed a similar change after spending time in Rio. Many lose their socially-inculcated fear of being in close proximity to men (and perhaps men of other races, too).
But do remember that upon return to America to KEEP YOUR HANDS TO YOURSELF!!!!!!!!!!!!!!!!!