There is a difference between maintaining a cordial working relationship, and being friends. I certainly don't go out of my way to be rude to my colleagues. But

There is a difference between maintaining a cordial working relationship, and being friends. I certainly don't go out of my way to be rude to my colleagues. But I don't pretend to be their friends. To illustrate the difference, my friends and I often have rather vehement political discussions. But I would never try to have such a discussion with my colleagues. It would just get in the way of getting on with the work at hand, and would potentially lead to hard feelings that would lead to difficulties at work later on. In some ways, I find it's more enjoyable to not be friends with my colleagues; to keep my personal life and work life as widely separated as is feasible.