So that you can adjust the gameaudio and voicechat volume separately on the headset.
How to:
Set the windows audio output of games/media to "Astro a50 game" but set the discord, skype, teamspeak etc.. output to "Astro a50 voice". Now you can set the perfect volume balance between voice chat and game audio on the right headset. I think this does not work for games with their own/integrated voice chat like PUBG, Arma and Fortnite.