I've only taken one IV so far, but I had the same experience. I was actually surprised by how other applicants went about background and lighting, given how often you see this discussed in here, the spreadsheet, and youtube videos. But it's just another case of selection bias, just like with USMLE scores. For me, background and lighting are the most important. Even with great audio and video quality, I wouldn't be able to pay attention to someone when there's a million things going on in the background.