A lot of libraries, JQuery, Lodash, Angular, Vue, React, Bootstrap's JS, module loaders, etc aren't simply offering "improved interactivity" they're offering core functionality. In essence the site runs on these libraries, if you remove them there's nothing left to regress too.
I've worked in several companies and never seen progressive enhancement used. It might have made sense back in the IE6 era when JavaScript was just for whiz-bang, these days JS libraries are holding the whole site's data context/state and generating Ajax as needed (Vue, Angular, React, etc). That's core, there's nothing progressive that can be removed from that.
Progressive Enhancement only makes sense for small toy sites or for academics to play with. Even Netflix's famous examples are about web services going offline, not losing core JavaScript libraries.
There are apps using browser as execution environment and there are websites. You wouldn't expect a client-side drawing tool, WebVR game or real time visualization of blockchain transactions to work without JS enabled.
However, you can easily expect a social network, mail client, news page, task app, and to some extent even things like IM to work with no JavaScript. "That's core" is just an excuse for poor architecture - it's only core because you chose to make it so.
There are apps and there are websites, with only some small part of grey area in between. If you're a web developer wanting to use newest, greatest trendy tools, you see everything as apps, despite of common sense suggesting otherwise, and you end up with no progressive enhancement for no good reason. When you take it to extremes, you end up creating such abominations like the old SPA Twitter frontend, spinning the fans of your laptop for 15 seconds just to display 140 characters of text, because "the core" is implemented as AJAX calls and fully rendered client-side.
We're talking about large organizations. No single developer is making these decisions. And the question is about resource allocation, if the choice is between improving the core experience or implementing an experience that <1% of our users will ever see, the choice is easy.
> "That's core" is just an excuse for poor architecture - it's only core because you chose to make it so.
It is core because the internet has democratically made it so. You're speaking for a very vocal minority. We're choosing not to implement a special mode for people who self-selected to receive a broken web experience. Fortunately that same demographic knows how to resolve the issue they caused.
> no progressive enhancement for no good reason.
A richer user experience is a very good reason. If the choice is between making the site richer and more immersive for 99% of users, and leaving 1% of users who wish to be contrarian for no reason out in the cold? So be it. A worthy sacrifice, in particular as this 1% selected themselves for punishment.
You're welcome to pick and choose any arbitrary part of the web to disable, maybe JavaScript, maybe CSS, maybe font rendering entirely, maybe disable images, but it gets a little silly when you blame others for your self imposed breakages. You don't want it broken? Don't break it.
There is no choice. You can either make it properly, in accordance to best engineering techniques, that make it work good enough with those restrictions and still work as rich as you want when you don't impose them. Or you can make it broken by doing it the lazy way.
Also, there are plenty of reasons to disable JavaScript. It often makes the web browsing experience better, faster and more energy efficient. Sometimes you care about those things way more than any perceived "richness". In many cases, lazy webdevs and their broken code are the only reasons why it might be worse.
As to users choosing to run without JavaScript? We simply don't support it. We support IE8 and above. You cannot even get to our site using Windows XP due to errors in the TLS negotiation (to avoid SSL downgrade). If users choose to disable a core part of their browser that happens to be a core part of modern web standards, then they shouldn't be surprised when sites using that part no longer work.
We built Qantas’s in flight wifi portal using this same technique, a necessity to deal with providing users with an instant ‘web’ experience over a high-latency connection.
Toy sites or for academics? Hardly.
You gave two examples, one of which didn't even work correctly when regressed ("videos won’t play") and the other is effectively a toy site (login/terms of service portal).
When you're in the weeds developing complex data entry sites for large companies or government, you aren't going to write the page three times progressively, write three sets of tests, run userability & accessibility studies three times, and maintain all three for tens of years with bug fixes/enhancement.
What you're going to do is lock in your library requirements, and if the library failed to load you're just going to fast fail into a generic error message until the library is available. If for no other reason that it isn't financially feasible to do anything else.
Progressive enhancement of JavaScript libraries was dead the second we went to SPAs and had a library hold the page's data context/scope instead of writing web pages using HTML forms and refreshing every time you click.
