But we have file timestamps, permissions and other attributes. There could easily be a "file type" field too, that seems more natural than shoving this metadata into the title.
As I see it, a timestamp is "non-negotiable". The file was last modified on April 22, 2001. There's no difference of opinion, the time is what it is.
But the file extension partially reflects a user's intentions. A stylesheet named "style.css" is intended to be used by a browser directly, whereas one named "style.scss" is expected to go through a preprocessor, but the two might have the exact same contents, and I might decide to just change one to the other, and that's okay.
I take your point about permissions, which are expected to be set by the user. Of course, I actually run into problems caused by incorrect permissions all the time. Maybe it would be better to encode those in the file name! (Although I don't know how you'd do it without creating a mess, and potentially security issues.)
