You're presuming that you can do all the manipulating and creating of a file without being able to work with the file itself, which I have my doubts about.
Well, I'm not sure if this is what you mean, exactly, but...
I can take a photo with my camera, plug it in to the computer, import the photo into iPhoto (this is done by clicking the photo itself and clicking import - there's no generic "file" icon displayed or choices about where to save anything), then do some red eye reduction, maybe some cropping, and finally click Share/Email and send the edited photo to someone else. This is all done without ever having to care about any underlying "file."
But no-one is suggesting that we actually get rid of the underlying files. They'll still exist, so different programs can still exchange information that way.
The problem is more centered on the idea that a document is pretty much useless without the application that can read it. So why not make this link explicit?
Case in point. A friend of mine is in a band - they've just released their first album. Whilst trying to drum up some buzz, they distributed one of the songs on the album as an .mp3. Trouble is, the guy exported the song as an AAC, but he named the file blahblah.mp3. Then, iTunes and WMP both refused to play the file because the format didn't match the file extension. This sort of error should just plain flat out not be possible. It's a song, not a file, and it should not be possible to create grief by stuffing up the name of the object as the computer sees it.
You care about files because you have to, not because you want to. As a content producer I consider every abstraction that lets me ignore the fact that the project I'm working on is actually made up of tens of thousands of files in dozens of different formats an unequivocal good thing.
