Consideration for fellow man

Yesterday on a one hour train trip, couldn't help but notice how many people sat in the aisle side seat of the two-person seats, with their bag on the adjoining seat or just themselves sitting in a way as to indicate that they 'owned' the seat. People boarded the train, looked around and, seeing there were no vacant seats, had to stand for a great part of the journey. What is happening? How can people be so inconsiderate? There were plenty of seats available for everyone on board to be seated, but many two-seat sections were taken up by one (selfish) person. Are these people afraid of being contaminated by another human being sitting too close to them? Are they just not able to share? Are they wary of strangers to the point where they have to 'protect' themselves from others by placing a bag or other possession between themselves and others? What is happening here?
Of course I was too "chicken" to voice my concerns out loud. Imagine, "Move over, you selfish twit!" or (more politely) "Please remove your bag, so that others may have a seat."
Oh, dear! Are we becoming that selfish?  Talk about.."I'm alright, bugger anyone else!"