> If anything, I would lean more towards guessing that users are, more often than not, either ignorant or untrusting of URL contents, either because the URLs so frequently look like nonsense (arbitrary content IDs instead of meaningful names) or because they have already proven to be unreliable elsewhere on the web (deep links not as deep as expected when copied or shared).
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)
