While we're talking about things we don't need, let's include this change.
The fact is, for most of the last two decades we've already had a UI where users who don't care to attend to the URL don't have to, and users who care to notice can. What does this add? Nothing. But it does take away some legibility for people who care, and discoverability for people who might learn to.
99% of people using web browsers really get no cues from the path? Cite please. URLs aren't high tech any more than the address to your house is, and my observation is that even non-developers who are simply experienced browsers pick up cues -- even from barely legible URLs mostly meant to be parsed by machines. You don't have to be a programmer to observe that typing a string in takes you to a page, or that the string changes when the browser loads a change, and put together the address correlation until you start to understand what a URL is without even really thinking about it.
Or at least, you wouldn't have to be a programmer to learn to make that connection based off of simple observation skills if we kept the current model. If we move to this new hide-the-URL UI, probably you would (self-fulfilling prophesy!).
And sure, the web has lots of URLs that don't provide a lot of easily parsed cues. In the interest of being a little less selective, though, let's look at a few others:
Do people need to see these things? Nope. Can they derive utility from being able to see them? Yes. And they do.
When you stop by the local coffee shop, do you take note of what its address is?
The users have an idea what URLs are, they just don't care.
That's like clicking on a bookmark. But when you need to tell someone else (who is unfamiliar with the district) where that coffee shop is, or vice-versa, that information becomes really important. Hiding the path and showing only the domain is like telling someone "it's in California".
On the other hand, if the URL is displayed, then there will be many who take note of the fact that it changes whenever they click on a new link or go back/foward, and it makes them mentally associate "that piece of text" with "this page I'm looking at" - they don't even need to know the term URL to do that. It's a bit unfortunate that browsers don't have "Address:" next to it anymore, because that would've made this association so much easier (someone seems to have made the same observation almost ten years ago, although it was FF vs IE: http://cheeaun.com/blog/2004/09/address-label-for-address-ba... ). Having made that association, they can then tell you exactly where a page they're looking at is, and vice-versa.
Postal address? No, but I do know (for example) I'm on Main street, in that tiny alley one block west of 4th Ave, in the building just left of that weird giant sculpture of a bird.
I'm constantly aware of and can describe my relative location, even if I'm not always capable of expressing it using an absolute designation like postal address.
On the web, though, there is no such relativity. One website is not near or far from or above or below another. I cannot conceive of my location, much less express it, in any way but absolute address.
So: since I do not travel to reach places on the web, how do I know where I am? The address bar.
Similarly, ever tried to find your bud's house the first time in a subdivision, esp. at night? Those places all look the same and you drive past 4 times before you figure out one of the house's numbers and deduce it. The pizza guy the other night thanked me for having my number clearly displayed and lit, for the same reason.
Of course once you get into a building, it still remains annoying - I mean it's still not really obvious how the internal room/suite numbering works. That portion of addressing is totally up to the architect, and a lot of times is only intuitive after you know the space you're in (if ever).
Legible URLs are important when you need to decide to follow the link; once you're on the page, it's less important because there's bigger and more legible cues about the content right on the pages themselves then.