A URL is an address. All your mom needs to know is that if she goes to https://news.ycombimator.com/item?id=24156986, she will end up at something and she will be able to come back to it later, that's what's useful about it. And besides, there are URLs that are semantically useful, such as reddit's "u/username" or "r/subreddit" schemes.
Of course, the URL is being assaulted from two other fronts, with websites turning into single page apps and with social networks constantly making it difficult to share URLs.
I think that's what it comes down to: if you're just copying and pasting the whole thing, there is no need to show the user all the garbage after the tld, it may as well be totally random characters to them. You can still copy and paste the whole thing.
I'm not sure whether I'm in favor of this change or not, but I can see there are at least some valid reasons to do it.
Then the existence of the URL is still justified by giving the user something to paste. So what if the user doesn't know what every single part of the URL means? They know that this URL gets them to this page and that URL gets them to that page. It's visible cause and effect. Get rid of it and we end up with "magic" where copying "news.ycombinator.com" on one page will produce a different outcome from copying "news.ycombinator.com" on a different page. This is how it works on iOS today and I think that eventually, users who only interact with iOS devices will not know what to make of that.
Weo hide all complexity from non-technical users then winder why they don't understand the complexity that's still there underneath. I don't believe that we should continue doing that. If the problem with URLs is the URLs being long and scary, let's make websites with better and more readable URLs.
There are some cases, like with Facebook/Google/YouTube, where they add a bunch of tracking info onto the URL, obscuring which segments of the URL are optional vs. required.
But I think that's exactly the point, isn't it? To make it a lot less noticeable when you're being tracked. This change will enable a lot of URL funnybusiness that harms users.
Beyond that, just about everyone who has used ebay for a while only cottoned on to the item number being the magic thing that identifies an item for sale. Nothing remarkable in that of course as ebay has it everywhere, but then most go on to figure out that https://www.ebay.com.au/itm/Bathroom-Acrylic-Free-Standing-B... and https://www.ebay.com.au/itm/254579100447 are the same thing.
Shorter version: you say people don't notice patterns when they see the same thing over and over again. I've don't think I've met anyone under 30 who doesn't. And once they've noticed, they then exploit the patterns to their own advantage.
My assertion is that the vast majority of people do two things with the address bar: 1. Manually type in a web site address, but nothing past the top level domain 2. Copy or paste the entire thing
I think what you're asserting is that people look at them, understand them, and then apply that knowledge somehow. I disagree with at least the last part, and probably the first two to a lesser degree.
What percent of laypeople do you think have manually altered a URL like your eBay example? I've done the same thing with Amazon product links myself, but I don't know anybody else who has. I just don't think it's very common at all.
The laypeople are not idiots, they understand things, in particular referencing an item by ID.