People shouldn't be drawing conclusions from the URL (apart from the query string and the domain part, but that latter is a whole other story). The URLs are supposed to be unchanging and not break, and that's strongly incompatible with having them contain human-meaningful information. And in particular (though not exclusively) with using path-segments to communicate a tree structure for your website. Such tree structures are inevitably torn down and replaced over time on most long-active websites (especially those which are the public-facing homepage of a long-lived organisation), and the result of placing them in the URL is inevitably link breakage. Hiding the URL by default is therefore good, as it should help to prevent the user from seeking meaning in the URL or the site owner from placing it there.
And links (with the exceptions noted above) shouldn't contain meaningful information for automated use either: it's Hypertext As The Engine Of Application State, not Link Structure As The Engine...
(Tree-structured site guides are fine and useful means of navigating, by the way; they just don't belong in the URL.)