If there's one thing that's clear from visiting any news publisher's website, it's that news publishers are unable to build sites that are fast and mobile-friendly. But one things news publishers do know how to do is rig up their CMS to also publish to proprietary systems like Facebook Instant Articles.
The magic of AMP was that it tricked publishers into thinking they were publishing to one of those proprietary systems, when in reality they were building a fast mobile website! Because it imposed strict rules rather than just "faster is better", publishers could throw out all of the stupid, awful practices they'd built up around making websites. Can't use that bloated framework of the week, AMP doesn't support it. Can't give the ads department free reign to ship whatever third-party scripts they please, AMP doesn't support it. Don't worry, website team, we're not threatening your jobs -- AMP is just another proprietary reading system, just like Facebook's.