I rarely backdate a post, and when I do it's either because it's a new sticky post, or because I'm doing something with code that I need to test but need a public post (most recently, figuring out some CSS to display a message to logged out users only).

Those posts are of little to no relevence and I'd not want to see such things lon latest, if someone backdates they do so for some sort of reason, not wanting it on Reading pages, normally becausre it's a clutter post, is valid. I'd just assumed latest things wouldn't pick up something I backdated to 1999, and I suspect those that use the feature had done likewise.