I think mics and webcams suffer a simple problem: the person who enjoys the benefit of higher quality is not the operator. Indeed, the operator may never experience how they look or sound.
That might be true, but your reputation is at stake as well. For the same reason that you might wear a suit to an important meeting, you might also take steps to ensure that your video and audio quality are presentable when you're having an important meeting virtually. (Of course, once you've paid the cost for that, you can just do a good job for all meetings. Much easier than a trip to the dry cleaners.)
Not even just reputation. I have seen people with poor (often too soft) audio get 'snowed under' while trying to raise a point. It's much easier to ignore someone who is less 'in your face'. In that sense I think it's really important for effectiveness in meetings.