Different people will have different answers, but one of the most common thing I have heard is that it's basically another way that a big tech company was trying to control the internet.
Google started to basically require websites use AMP in order to appear in search results. This is a conflict because AMP doesn't support all advertisements, but it does support all ads by Google. This matters on mobile because people are less-likely to have adblock. So they weren't telling websites "if you don't use our ads, you won't show up in search results", but they were implying "if you would like to continue to make a living you will use our ads and services."