Unused services are always pure profit, and storage space is no exception. Providers can offer 100GB for like $24/year, because only like 2% of the subscribers will ever approach the limit, and so the extra space is never wasted but can be allocated to someone or something else.
It's like gym memberships, ISP/telco service bundles, and amenities at your apartment complex. Anyone not using every possible service is wasting money, but it's impossible to purchase a bespoke service, so essentially everyone will waste money because they're chipping in money for services that someone else uses more than they do.
Here at home I don't ever use the gym, the racquetball courts, the doggy-doo supplies, the laundry room, or a parking space, and yet my rent (everyone's rent) includes upkeep for all of those things. I'm subsidizing all my neighbors and all the wear-and-tear damage they put on those common amenities. Likewise, everyone who's paying $24/year for storage, or any business that purchases big multi-terabyte storage media, they're paying for unused storage space and giving profit. It's practically impossible to rightsize your storage media, and you never want it undersized, and you can't simply shrink them and reclaim the resources you invested, you just keep adding on new ones and replacing the malfunctioning ones. So nearly everyone always owns or rents more space than they can realistically utilize.
Furthermore, you'll notice that I specified "automatic" destruction of data by expiration date. Of course it is trivial to tag any arbitrary file with arbitrary metadata, but the challenge is to create a filesystem that executes automatic data purges on schedule, rather than pushing it into a rickety old handmade cronjob in userland. I've never ever seen a filesystem with such a feature, nor does it seem that anyone's interested in doing so.
And here I thought that computers were useful for automating business logic and easing the burden on human effort. And this is me, manually sifting through emails and photos in order to manually delete each one with 3 dialog boxes intervening. It takes hours, days, weeks.