As a Roblox developer, it is currently too hard to set all sounds in a game to a default SoundGroup, especially avatar sounds which are created in runtime and thus can only be updated by script.
If Roblox is able to address this issue, it would improve my development experience because it should be much easier to apply effects to sounds in the world by default, such as reverb in caves and muffling underwater.
If all 3D objects have a default collision group, all sound objects ought to have a default SoundGroup instead of nil.