You remember Akamai, right? AMP is just another CDN. Back in the 90s, when Akamai was fighting to establish themselves, you'd see tons of fetches from hosts like a123.d.akamai.com on big name properties like CNN. Nowadays it's pretty much hidden, and pervasive.
Google is attempting to entrench a reverse proxy cache the same way Akamai has for years. AMP is nothing new. The only difference here is that they make it obvious you're using a CDN, whereas Akamai is almost completely transparent and runs close to 80-90% of the traffic of the "open" web -- you just don't know about it.
How is Akamai optional for a user? If you're saying that it's optional for publishers, then your argument doesn't make sense since AMP is optional for publishers as well (I mean, the author disabled it and all).
Google is attempting to entrench a reverse proxy cache the same way Akamai has for years. AMP is nothing new. The only difference here is that they make it obvious you're using a CDN, whereas Akamai is almost completely transparent and runs close to 80-90% of the traffic of the "open" web -- you just don't know about it.