The hope is that social pressure will encourage more and more companies to participate.
Oof. Yeah, nah… Capitalism doesn’t work that way, and if by some miracle it did, the rug would get pulled sooner than later. Most businesses don’t even pay their employees fairly, and you expect an optional expense to be sustainable?
As others suggested you don’t need all your historic mail on your mailserver. My approach to email archival is the same as all my historic data — a disorganized dumping ground that’s like my personal data lake, and separate service(s) to crawl, index, and search it (e.g. https://www.recoll.org/)