I can offer what I've observed in my own life. I noticed that after college, the group of friends that I had did not act like this. They were more adult, more considerate, and didn't consider it okay or "cool" to be hurtful towards other people in the group.

I'm not trying to speak for everyone, but I think that often it just takes time for people to grow up and leave behind certain group behaviors. People will often behave worse in a group than they will as individuals.