@Lea Yu,
Maybe it helps if everyone puts in where they are from....
I am from the US - Boston area. I read on the subway and other modes of transportation - unless of course I am driving. I see many others using their mobile phones, watching videos, playing games, etc. And often times talking to others.
I used to always use an actual book, until my family gave me a nook (tablet reader) for my birthday - now I read books, but in electronic format. If it is very crowded, I might not take it out. And have on occassion spoken with other passengers even those I do not know.
But I love to read - not everyone in the US/Boston area does - so I guess you do whatever you like.