I'd guess what's holding that back is that a) that fee is not necessary for them to use it, and b) it's hard to fight for paying money that's not technically necessary, and c) getting a license for anything approved can be a pain.
What I don't think prevents this is that companies (even startups) think it's too expensive.
But for a corporation undertaking the obligation to pay any amount of money is not trivial to do. Someone inside has to justify the expense, probably write a document about it, depending on the corporation all kind of hoops need to be jumped, decision makers convinced, checks and gates passed.
It is probably not meaningfully harder to do all of these for a $50k yearly licence than for $5 monthly licence.
Still, the other point (why pay if there is no obligation) is a bigger obstacle. One obvious solution is to provide paid extensions on top of free core product, but that might lead to forks if enough people are interested in the functionality and not willing to pay (/ use proprietary software).
I believe the future is in "fair use" licenses - those that grant users freedom to use for their (non-competing) business and to repair as needed, but that allow original developers to charge money for extra features and for services without worrying that competition will undercut them on market (without supporting the product).
I'm following the "cloud protection" licenses and hope that one of them gains enough traction to become a serious contender to FOSS.