At the moment, holding data about someone is not a significant recurrent cost, but it is a liability in the form of a risk that could get you in serious trouble if you get something wrong. However, that particular business risk doesn't tend to be recognised by many many organisations. It should be.

If they can afford to be ignorant of the risks, it's because the liability is not high enough. Gotta raise the liability until they start doing what we want them to do by default. Private information should be an existential risk for them. They should be deleting every last bit without even asking, not sucking up endless amounts of it without consent.