TL/DR. Taxpayers fund research that they cannot access without additional payment.

Same thing almost occurred with weather data (https://www.bloomberg.com/news/features/2018-06-14/trump-s-p...)

Simply a system with broken incentives (publish in these longstanding journals or perish), a system designed to exploit those incentives (pay us to publish in the aforementioned journals), and a group of humans who have little personal incentive to stick their necks out (e.g. grad students and professors).