My husband has a pet peeve. If someone can’t be bothered to say, “Good morning,” or otherwise acknowledge you–even a “Hi!” will do–he thinks poorly of that person. If someone always greeted him, he maintains a good impression of that person.
I always try to say good morning to the people with whom I work. I also try to say, “Have a nice night,” when I’m leaving.
Being friendly doesn’t take a lot of effort.