If you have to make a chart with tons of volume adjustments, you just as easily make the adjustment yourself. It should all be consistent and normalized.
While you have a good point, that can be a very inefficient workflow.
When it comes time to tweak the sounds' volumes in-game, it can be extremely cumbersome to have to check out the asset, edit it, and then check it back in just to make it a bit louder or softer. Also, if that wave asset is used in multiple places, then you've unintentionally changed the sound level elsewhere in the game of that sound, which might have been fine in that context.
it can be far easier to simply tweak a constant in the game code or a table somewhere. When you're in the "iterate/try" loop, it's waaaay faster and is also less prone to errors (i.e. using the wrong version of the wav file).
So having to go back to the source asset and edit it whenever you want to tweak the volume is not a real good solution.
Short of a proper tool, I try to have games use a data driven table that maps GameEvent to [WaveFile,Volume] as a bare minimum. And I (as sound designer/composer) own the wave files and the data table.
Ideally, you would deliver the sounds roughly where you want them, and then have the ability in code (or data-table) to tweak the volume levels up or down from there without having to change the wave assets themselves.
Btw--its for reasons like this that tools like XACT, Fmod, WWise, etc were created in the first place :-)