I mean like why?

I think it's just so hilarious but sad and depressing when a student is in the dinning commons and they are sitting be themselves with 3 other chairs. Then a another fellow student is looking for another chair to sit on while they are eating with their group of friends. The student comes to the one, thats sitting alone and asks " is anyone using this chair?" ( of course the fuck not) They take the chair while the other student is STILL sitting along eating! WHY! Can't a student say " OH HEY you are welcome to sit with us" Instead of just taking their chair and make them feeling lonely then they already are!