What's the point in what you hear there even when you talk to the chat on twitch for example. Do you have the headphones on or if you are playing games it is because you do not want to hear your own voice
The sound of the game is just better. If they are good headphones. And you block out the disturbing noises of your environment.
Loudspeaker and microphone do not get along so well
In addition, you can hear much better with headphones and you don't disturb roommates, neighbors, etc.
This is done e.g. To hear the audio output of the game and / or people with whom you are in voice chat. If you instead let the audio output go through loudspeakers, it would usually be picked up again by the microphone. As a result, viewers would hear the sound twice, which is rather unpleasant.
Less ambient noise and you can hear it better, but much more important… No feedback in the sense of the sound is picked up again by the microphone.