That's exactly the point. It does matter to people that the MP3 encoding method be supported. ATRAC8, the current encoder Sony is using, is not widely used and nowhere near as mainstream as MP3. Many users have MP3 file collections already, and to change these files into ATRAC8 would cause further quality loss, and (assuming the MP3 files were deleted) prevent the user from moving to non-Sony devices in the future without another re-encoding session back to MP3.