[vacri]

This is probably due to the specific nature of browser upgrades, which is the reason why firefox and chrome went to 6-week autoupgrade schedules for clients: people expect a hell of a lot from their browsers; troubleshooting a fractured version environment in such a complex field is next to impossible; important security updates need to be pushed.

So you end up with two main releases for the browser, one is the standard one that updates every six weeks, and the other has a more stable 'extended support' environment that just gets bugfixes, for places that can't easily deal with changes very often (like a business or education SOE). Debian stable usually lasts for about two years, and modern browser releases would find that impossible to support.