AMP is, to begin with, Google exerting its market power to extend its control over others’ content. Facebook is doing it, so Google has to.
As a consumer, I actually love AMP. Everytime I click a news link on mobile and am taken to AMP, I'm relieved to be free from the extremely distracting original websites.Google has done a lot of exciting work on open standards like JSON-LD [0] and Microdata [1] to bring a better experience to both Google search results and Gmail. I love clicking the inline "Confirm subscription" button [2] instead of opening emails from Mailchimp and searching for a link. I'm not that scared of the future becoming locked into Google. I believe they'll improve upon and create better standards for emails. Most things aren't entirely altruistic, and that's OK. Gmail being an early adopter to these standards is a good enough reason for them.
[0]: https://developers.google.com/gmail/markup/reference/formats...
[1]: https://developers.google.com/gmail/markup/reference/formats...
[2]: https://developers.google.com/gmail/markup/reference/one-cli...