Comment by hnbad

Because the US has laughably weak privacy laws and most Americans snicker at the EU GDPR because of "cookie banners" (which btw isn't a thing - most consent dialogs are non-compliant as they shouldn't serve to just inform you but to actually obtain voluntary, revokable and specific informed consent) instead of thinking about what it means to actually have a fundamental human right to privacy and ownership of your own data or not.

They keep the samples for the same reason US tech startups keep deleted data and track seemingly useless behavior. Because they might find a use for it someday and there's literally no law preventing them from doing it.