He does not want to play to her vanity. Other men have chosen not to dance with her, and he is not in the mood to go out of his way to make her feel better about herself--assuming she is embarassed or otherwise hurt by being without a partner. There may be a subtle hint that the "other men" were of less social consequence than he, but this is debatable.

I think the residents of Meryton, etc. interpreted his behavior as being snobbish, but are we ever told by Darcy or the ON that it was? I might have forgotten something. If not, I still think it is open to interpretation. As I have written elsewhere, I think Darcy thought the behavior commonly required at a ball was beneath him--not necessarily the people in attendance. We are told he was continually giving offense, so I don't think the Meryton crowd was being treated differently than most other assemblies of strangers.