Features like offset, storyboard, hitsounding, bg video, combo colours, background dim, etc. already have both local and universal settings, and I think that volume deserves it too. Different players and mappers have different preferences for effect and music volume, in a player's perspective arguably effecting playability as much as offset, an example being that it's fairly widely known that louder hitsounds will equal higher hit accuracy for many players. In a mapper's perspective, with volume being adjustable in the timing point menu, and the volume of the mp3 to be taken into account, there's no way that so many different mappers and so many different maps can have a reasonably equal balance of music and effect volume. Although playing a map for a bit and changing the volume after testing the waters may seem trivial, the option for local settings have already been given to many, and in my opinion, less important settings it should be time volume is given the same treatment.