I think its possible to like and be affable with people at work. You can respect them and chat with them.

But I can see the argument where you wouldn't want a "work relationship" to turn into a "friendship".

Friends might let things slip - and then there's resentment. That expectation of diligence might fade slightly in a real friendship.

I can see the argument to keep it professional in most cases. Having a work network and a friend network is an option.

Just make sure to maintain both...