This is only true if the cost of storing user data is greater than the profits it generates. When companies are allowed to sell out users and punishment for data leaks are just seen as the cost of doing business then why would you not store whatever data you can get your hands on?
User data is only an asset if your business model demands it, like Google and Facebook. If you don’t have, and won’t create, a way to monetize it then yes, it’s strictly a liability.