Yup it’d be the cause for it most times, that’s if you aren’t doing anything to the audio server-sided.
Is there any downside if we do not allow people to change it and just always enable it?
Always ENABLED will be fine for many user cases but if you fail to offer the options those with pro-audio gear would get quite upset with you so I’d always offer them.
You can expect this varying setup between users can cause some users to not be heard if they’re overly echoing. This is echo cancellations purpose; noise suppression isn’t supported on all browsers but will hide your fan sounds. The auto gain control will make quiet users sound much louder. Have fun.