Marketers want to make money, and right now stuffing emails with images in favor of proper layout is the only easy way to do it.
Of course google also wants all of your email googling its way through their servers.
There is already a Gmail placement for AdWords ok the GDN. However for the most part, if I as a marketer send emails to my customers, I can be more or less certain they will get delivered if my deliverability is high.
What I see Google doing here is gradually exerting control until they tell brands "hey, you know those messages you used to send to customers for basically free? Now you need to pay a dynamic price we control in order to get any "organic" reach."
And just like that they will have turned one of the most valuable, scalable and cost effective marketing channels into another large revenue stream for themselves that gives them even more leverage over marketers.
Kinds of genius when you think about it.
That's already happened with GMail, hasn't it? The filters for Promotion, Social, and of course Spam already control what/where users see (and it'd be trivial for Google to charge a fee here based off visibility of Promotion-categorized messages).
It's still in a linear and usually legible way, of course, and I think it's arguably user-friendly if imperfect. Doing what facebook does with feed/status updates with email would be absolutely ludicrous, it would make GMail a ghost town overnight.
I don't think introducing ads into the feed is as ludicrous as you say from a business standpoint. If done properly, I could see Google avoiding a mass exodus while simultaneously opening up more inventory for them. In some ways, I see Inbox as a test towards this vision.
My broader concern is a fundamental shift in the ownership of a customer/user relationship and the cost of reaching them. In today's world, you pay a fixed price for your ESP, and then some CPM rate for volume typically. Your costs are known, often negligible, and entirely under your control. Likewise, as long as you follow best email practices and nurture healthy relationships with those on your email lists, you have an expectation that your email will land in their inbox if they want to receive it.
That is similar to what FB had back in the day when someone Liked your brand page. If you posted, they would see it assuming they scrolled through their feed enough.
My fear is that Google will change that dynamic such that you cannot be guarantee to reach your audience (even if you have great deliverability) without entering into an auction and paying a constantly changing price that presumably will always increase as they maintain control as the new gatekeeper of that customer communication.
That is by design. Email is not an image viewer nor is it an HTML browser. It is a plain text medium.
It's an exaggerated version of the image-heavy email newsletters - these are obviously nice for the marketer, but the messages that I want to receive are not like that, they don't need this feature, it's only useful for those who want to steal my attention.
If marketers really need it, perhaps it could be a useful way to automatically forward any messages using this technology to spam.
Somehow I expect that GMail's search box will get a "usesAMP:yes" or "content:AMP" filter or something. It has a lot of filter keywords like this[0], undoubtedly they'll add it.
You can easily add a filter rule to automatically mark all messages matching a filter as "spam".
If enough people do that, they might get the message. (and probably just remove the search filter option, sigh)
[0] come to think of it, GMail's search is a delight exactly because almost still kind of works like how Google Web Search used to work back when it was still good, a mere decade ago ...
That's a feature, not a bug.