A lot of people, especially those new to cycling or those who haven't ridden for a while, are uncomfortable with taking their hands off the bars. I know when I first started again after not riding a bike for a few years I "snobishly" refused to wave to a few passing riders. So that could be a part of it.
The guys in the OP seemed like ******bags though, but it's hard to say if the guy was being funny, or if there was previous history that the OP doesn't know about that made the comment relevant or whatever. Also, ******bags are everywhere anyway, so who cares