Interesting. You still use this feature? I always thought YouTube and the like still included it on their sites as a throwback to an earlier time, or something. I always use the software on the playback device itself to control the speakers.
Volume controls are important! Some examples: you are on a VoIP call but want background music. You have to listen out for some notification and the front music can't be too loud. You work with other audio files e.g video editing but don't need to be listening actively. Any media-multi-tasking situation, really.
I almost always play several things at once. The standard is to have Twitch or Netflix/HBO on one monitor and a game on the other. Without specific volume controls it would be a disaster.
