If you're into the collectability and provenance of a bike, where a frame was built matters. Or maybe if you get a kick out of researching it & knowing, like sports statistics. It must matter to a lot of collectors, since I've read here about scammers forging Colnagos, etc.
The implication of a sub-contracted or off-shore built bike, of course, is that it's done to meet cost or production volume targets, and therefore the quality is not as good. That, and it doesn't have the "romance" of coming from some Italian craftsman's shop. This is all relative, back in the 80's Japanese bikes were considered copies and not all that great, now the vintage ones have respect.
Old Italian bike= collectible,even though they made crappy ones, too.
New one, actually made in China with spotty quality, and a re-licensed or a made-up, Italian style name= (perceived as) junk.