This guy asks about archival - https://superuser.com/questions/374609/what-medium-should-be-used-for-long-term-high-volume-data-storage-archival
They say to buy a 30TB LTO-8 tape cartridge for $79 - https://www.networkworld.com/article/3638116/why-aren-t-optical-disks-the-top-choice-for-archive-storage.html
ROMs would be useful for storing lots of data for long periods of time without corruption or freeing up space on your SSD for more hot data, that could be automated. They should be cheap and compact. These are useful properties.
Because capitalists are incapable of long-term planning.
Think about how much data sits out there without every really being edited/deleted. So many large datasets including videos, revision systems, and lots of records being taken including blockchains. I wonder what percentage of the data humans put out and store can be comfortably be placed on some cheap scaled ROM like this.