Culture bubble

I was on the train the other day and started thinking about what I have been noticing all throughout my stay here: people keep their distance from other passengers when they're taking the local transportation

Case in point: there are two types of trains where I live (in Sakanoue).
One type of train come in two-seater benches while the other type has long benches (cushioned, of course) on both sides of the train.
In both types, passengers tend to sit a bit apart from other passengers
It is especially evident in the trains with two-seater benches (I don't know how else to call it)
Although each bench can seat two people, not many strangers share the same bench in the train
I remember one time I was sitting in one of these benches and the seat next to mine and the two seats in front of me were unoccupied. Still, the high school student who boarded the train after me chose to sit on the floor instead of occupying any of the empty seats.

Ever heard of the term "culture bubble?"
I'm not sure if I got the term right, but the term essentially describes the distance a certain culture of people feel comfortable with when they deal with other people
For instance, if it were the same train in Taiwan, all the seats will be filled
If it were the same train in the Philippines, the two-seater benches would seat three to four people. LOL

I'm not exaggerating.
One time I went back to the Philippines, I was waiting in line at the airport and the person behind me was practically leaning on me!
I took a few steps forward and again she came closer to me like bees on honey!

I guess I have a way bigger bubble than most Filipinos after living outside the Philippines for so long...