PS: Not intending to be sarcastic.
PS2: I work for google, but not on something amp related.
Which leads to the question, why is google doing this? They, you, could easily promote AMP pages while not masking the real URL! The answer is simple, profits over what's best for users.
Edit: I just did a search to find the CNN interview I mentioned, copied the URL to share here, and look it's a google URL. WHY? https://www.google.com/amp/s/amp.businessinsider.com/trump-v...
I hope this AMP experiment is soon over. As someone already said here, the web is confusing as it is. Google used to want to make things clearer, better. AMP is not. It's fixing symptoms instead of causes.
Well, that explains why they wanted Chrome to hide URLs.
Different teams inside a business can have coordinated long-term goals.
Regardless, their master plan clearly shows "Redesign HTTP", "Browser", and "Next generation web (Fish Pod)" as precursors that lead to "Private Internet", "Walled Garden", "need more cache", and "NEWSBANK".
I run a WordPress blog. From the documentations of Google and WordPress AMP plugins, I have always thought that the user will be directed to "originalurl/amp" on my domain when they click on the Google link on their phone. Now that I see it's a Google domain, this is really weird.
Perhaps to allow the content to be served from a CDN (over HTTPS), without requiring the site to CNAME over their domain to Google.
If webmasters are willing to CNAME over their domain to a caching proxy, then a less intrusive design is possible, such as the one recently announced by Cloudflare.
Money. Amp vs adblockers
Do you really want to go down the rabit hole of a browser displaying a different url than what you are viewing?
Of course you wouldn't mind, since, as you've said elsewhere that you work at Google.
"It is difficult to get a man to understand something, when his salary depends upon his not understanding it!" — Upton Sinclair
Such really simple syndication technology could even have a catch TLA. I can't really think of one, but I'm sure there is something.
That said, i think people disable JS in general for this reason.
Why doesn't Google drop the URL masking while keeping all the real benefits of AMP? The answer, profits over people. I say this as a long time fan of Google, but this AMP stuff is where the "don't be evil" tagline turned into a joke for me.
AMP itself allows for fast loading which is true, but to support opening pages in "zero loading time" you still need pre-loading since fast loading still means non-zero loading time. To get pre-loading working in HTML you need to 1) load the iframe of the page in the background, then 2) when the link is clicked, use history.pushState() in order to manipulate the URL to appear you have moved to another page. Unfortunately for (2) the Web History APIs need* both URLs to be on the same domain so Google has an excuse that they need to change the target URL to be under Google for this to work.
Also Google wants to present the scrolling UI that allows you to browse to other articles in the search results (potentially from other domains). This can't be done if you have completely switched to the original website.
See this link for more discussion https://github.com/ampproject/amphtml/issues/6210
Personally I find this misguided at best, an excuse at worst. A fully compliant minimalistic AMP website (or even just a simple site that doesn't use AMP but follow best practices) will load incredibly quickly even without pre-loading. It's disrupting a lot of security and UX best practices (by replacing the address bar with "google.com" domain) just to achieve a very minor improvement. Furthermore they control Chrome. It's not too hard for them to push forward a web preloading standard and start implementing in Chrome.
Edit: Also for the scrolling UI it seems like another way for Google to push more engagement to their site rather than the target URL. It kind of runs counter to the open web nature IMO because there are innovations that helps previewing links already (e.g. iPhone 6s/7 3D touch) and it's the kind of behavior better implemented in the browser itself.
Apple: These article webpages are annoying - let's add a client side button to make it readable.
Google: These article webpages are annoying - let's force everyone to grant us a royalty-free license to their whole website.
 The real problem might be that Google results are "getting bad" - a thing people bring up all the time but which can only be measured individually.
So people tap the first 3 results and don't get the info they were looking for. On top of that it's slow af so people are wasting time. Now Google serves up faster pages so they'll tap through 4 or 5 results.
So why not fix the real problem instead?
 Yeah it's optional but only to a point. First the spammiest blogs implement it and they get a free pass to partially skip the line. Then some bigger sites implement it and even things out. People here are rightfully afraid that within 12 months you can't even hit page 2 without AMP.
Check the link rel canonical tag. Obviously not ideal but nowhere near "impossible"
Your average user (who doesn't necessarily know anything about software) doesn't really care about 1, and probably doesn't care about 2. They care about speed of the page, data consumption of the page, and maybe the look-and-feel of the page (bloated vs sane).
When I say HN user, i mean technically informed and most often skeptic people.
The distinction matters.
If I search for weather, lyrics, or other common sites, the top results are always slow, bloated, JS-filled nightmares. Yet the sites that are quick and small are never to be found.
Maybe they do and they need to weight speed higher. I don't know, but I know that I don't ever seem to get fast loading results.
This feels too much like creating a problem that you want to be able to step in and solve.