There was a previous discussion on HN that helped me understand the value of Google being "the bad cop" and making AMP restrictive. Before AMP, you'd have product people and ads people demanding to add all these bullshit ads and trackers to pages. Engineers would often try to push back with the performance argument, but it was a difficult argument to win (ads people could argue, "well, it doesn't really slow down the pages that much, and look at this revenue we get - maybe you just are coding it wrong when you're including the ads code!") With AMP, the discussion is very simple: "Sorry ads guy, I can't add your bullshit ad network JavaScript because it's not possible with AMP. You know Google favors AMP now, don't you, and you wouldn't want to be the guy responsible for a shitty SEO position because we didn't use AMP, do you?"

I'm not part of google, but they had been doing that for years, and still nobody was working on speeding up their sites.

Because that would not achieve the actual goal: to get people to stay on Google's properties, preferably without an ad blocker installed.

Note how over time more and more of the things that Google used to simply point to are served by Google directly. AMP is just another element in that strategy.