I agree that "average" depends on all sorts of things, and it is mostly useful to use to compare your own rides, but as a new(ish) rider I do like to have a sense of what others call average. It's not so important when I'm riding by myself, but it's nice to know what the averages are of typical group rides (even the slower ones are faster than I tend to go on my MTB). Not that I don't already know this since I'm rarely the one passing other bikes on the bike paths