Also, old-school is still the dominant way with how small sites are hosted, in terms of number of hosting providers who offer cgi hosting.
Also note that you'll often see a PDF generated on the fly with a long, difficult to parse URL.
Take up your second point with the W3 or whatever, to be honest if tlds weren't so important for phishing and whatnot it would probably be fine. I think some browsers have started doing that anyway. You overestimate how tech savvy the average user is, and by extension you overestimate how much the average user can keep track of all this complexity. Do you think most people have heard of .info or .xyz?
I think users are (rightfully) distrustful of URLs in the general case, but a URL having a file extension is actually a pretty good indication that it's a simple "does what it says on the tin". (Imgur changing their .jpg URLs to have more complex behaviour caused a pretty big backlash, for example)