I'm not big on small talk, or very good at it for that matter. I remember starting a new job where I was sat next to a couple of people who I quickly realised I had nothing in common with. Sat there all day in front of a computer. One of them often was away from her desk. The other just liked to talk utter childish rubbish and wasn't really interested in what other people thought. After a week of me being very quiet and not starting any conversations, he literally shouted 'SPEAK!'. I laughed it off, and placated the little **** a bit more from then on. It was a long year though.
Sometimes people are quiet because they are surrounded by morons.