Just because Android or iOS have some features, does not mean WP can’t have them. Just because other OS have multiple volume settings means WP8 can’t have it? Should it remain like a rotary phone with a single volume dial? Should we give up pinch to zoom or swipe just because other OS had it first? Very immature attitude on some people here…
If I correctly recall there was a sticky post by Dave Blake that used to summarize the top features users wanted implemented in WP8. A file manager was one of them. The sticky appear to have been replaced by PART 2, and no longer has a summary.
People that use the phone as an entertainment device can likely live without one. Once you go beyond that it’s hard to do without a file manager.
Simple task: I want to take an email attachment, save it to the phone, and then re-attach it to an new email. May work for media and Office files, but won’t work for PDF or other type of files. For the PDF file, you need to open it, then separately go to the PDF app, open it, upload it to Skydrive, then you can email a link, but not a file. With other type of files, such as .dwg, you have no options.
I also have friends that won’t switch to WP for not having some (business useful) features, the File Manager being one of them.