Prestige only has value if the community upholds it with integrity and warrant. The journals are fundamentally looking to protect their business model and their attachment to the community. Thus the journals' prestige becomes significantly diluted (and with warrant).

Publication prestige originated in the publication's crucial role as a discovery mechanism before the Internet. Now there's a much better discovery mechanism, and the community is adapting well to it. If publications had the community in mind foremost, they'd similarly adapt.