Well, in many photos, we like to stand in front of tourist landmarks as a sort of proof that we were there-- the ol' "This is me in front of the Eiffel Tower" shot. You can't simply download these photos off Flickr, so it makes sense to take these pictures. But, assuming we don't have some great photographic abilities, why do we spend time and energy photographing just the Eiffel Tower itself when so many great photos of it are already available?

I think it's because we get satisfaction when we produce an image, even when it's (sometimes highly) imperfect. It's human nature to hold up something we've created and proudly say, "I made this. Sure, maybe others have done it better, but this was what I did."

And others enjoy seeing what we've created as well (rather than just where we've been), even if it might lack the polish of the work of someone more talented. It's the same reason your mother was always happier to receive a hideous hand-made card on Mother's Day rather than a beautiful one that could be bought from the store. (Well, up to a certain age, I guess.)

If we were really only interested in showing people where we've been, we'd print out a bunch of photos from Flickr or upload a bunch of stock photography to Facebook. But we're equally interested in that "I made this" feeling, the one that comes from showing others-- and ourselves-- how much beauty we can create when we give ourselves the chance.