> So why would we really want to delete past data? From this standpoint wouldn’t deleting data be similar to trying to cover up the past?

This assumes that data is always true and accurate, which is not always the case. Say Bob was convicted for pedophilia but a couple months after the charge was retracted because it was an error. Now Bob can’t find a job because “the data” says he’s a pedophile, even if he’s not.