They just like doing something in a manner that you don't. Not much different than anything else. Are we all supposed to act the same and do the same as each other?
Not that I don't understand partly. We had a organized group ride last Saturday and had three or four pacelines of not quite a dozen riders each blow by us like we were standing still. Some of those dropping off the front seemed to miss me by about 3 inches which was a tad annoying.
But why should I be concerned that they don't ride as slow as me?