Like almost every MediaWiki feature, there's a massive pile of Wikimedia drama behind it. They went through at least three major iterations, almost all behind the scenes, for exporting content for offline viewing, including PDF at all stages, and eventually kind of gave up.[1][2][3][4]

This also encompassed the mostly ill-fated PediaPress system to get printed books of wiki content collections, the Collections MediaWiki extension,[5] and various back-end rendering engines that came and went (some without ever being fully deployed in production).

All to have a link that, in the span from OCG to Proton, was made mostly redundant by browsers implementing "Print to PDF".

[1] https://www.mediawiki.org/wiki/Offline_content_generator

[2] https://www.mediawiki.org/wiki/Extension:ElectronPdfService

[3] https://phabricator.wikimedia.org/tag/proton/

[4] Confusion over knowing who owns or maintains the PDF service: https://phabricator.wikimedia.org/T247310

[5] https://phabricator.wikimedia.org/T256071