The bandwagon effect

The bandwagon works on at least two levels. First of all, it tries to give the impression that a lot of people are doing something or supporting some position; then it suggest that the judgment of the masses is sound: If so many people are doing it, then it must be right (see social proof). Second, and more important, the bandwagon is an emotional appeal to our need to belong. We don't want to be left out.

— Robert Gula writing in Nonsense A Handbook of Logical Fallacies