Why pay money to make a better product when you can pay zero money for a worse product and no change in subscriptions? What are your customers gonna do, go get the paper somewhere else?
They can of course choose short term profits over long term viability, which wouldn't be all that surprising, but that changes the explanation from "more profits" to "short-sightedness/incompetence"
In addition to the high seas we've got a plethora of preprint services. Between arxiv and bioarxiv alone you can access a decent chunk of the modern literature. What we need at this point is for institutions to require uploading all publications to one of a handful of officially sanctioned preprint services under a CC license and to strictly forbid publishing with any venue that objects to authors disseminating a CC licensed version of the work.
But they could adopt an official policy of all publications being CC licensed and uploaded to at least one of a few officially sanctioned preprint services. That would do a lot to undercut the publishers going forward.
At this point a lot becomes open access after a few years anyway. The issue is historic papers but all of those can be reliably found on the high seas.