To me it's just tedious to say hello and bye, especially if it's someone I know I'm going to see again the same day, or probably the following day. I don't really see the point of it. But, I work in sales so I have to do it. Hello, how are you, the whole bit. It's annoying. I would rather just get to the point of the conversation.
Where I live, people are very friendly and some will get really offended if you don't greet them. Not just people you know, but people you have never seen before in your life expect to be greeted like they are your best friend. One day I was walking out of a store, and a man was walking up to the door at the same time and he greeted me. I gave him a nod but I had something on my mind at the moment and I couldn't get any words out. Before I quite made it to my car, I heard the guy say in this nasty way, "well hello to you too!" and I looked over my shoulder and he was just standing there on the sidewalk glaring at me. Good grief, I am not obligated to speak to everyone I meet. I was glad I hadn't said anything to him after all, if he was going to act that way about it. You just can't tell what people like that will do.