xkcd

People usually don't log stuff that they see every day. So a person who lives in Oregon (statistically more likely to be in doug-fir country) goes east and notices that a different tree predominates and they want to know what it is, they'll log it.

Personally, I log stuff that I don't normally see cause there's a chance that it's either: a rare native plant, a native plant on the edge of its range, or a non-native. Those are all things that I'm less likely to know off the top of my head, and I think it's probably more important to tag for scientific purposes.