I'm always suspicious of people who don't smile. I try not to be judge-y (I know that's not really a word) and make assumptions of people. Everyone has a bad day and perhaps my first encounter with someone is "one of those days," so I try to always give the benefit of the doubt.
However, when I've seen someone several times and notice the pattern, I'm not sure what to think. Part of me feels sad that they must not have much in their life to be happy about. Part of me gets a little bitter that they're raining on my parade. Part of me thinks they're up to something. In reality, it may not be any of that. It may just be their personality to remain stone faced and not show emotion. My point is - people who smile are more likable.
If I meet someone and they display a big smile, I feel comfortable. True, the person could be an axe murderer. If I am just being introduced to them, I don't know anything about them - yet. But, it makes the introduction much more pleasant. It makes people want to interact with you when you smile. It makes you want to get to know them more. Unfriendly people often don't get the same chance.
One of you boys - you probably know who you are - are hard to break the ice with. You shy away from introductions and people. You often don't give people the chance to get to know you. But those that you do open up to know how wonderful you are. When you smile, you totally light up the room. All of you do. A smile is a beautiful thing. It's a chance to show yourself and give incentive to others to get to know you better. Happy people smile more. Or maybe people smile more because they're happier. It goes hand in hand. Make an effort to smile and much as you can. It's worth the effort.