People who have video calls throughout the day constantly. I don't want to have to mess around setting up my phone on a stand and getting it connected every time I need to do a meeting.
I would sound a slight note of caution there, in that AFAIK not every camera has clean HDMI out and there can be challenges about powering cameras for longer periods of time (if needed).
It is a good option though if you need higher quality. I'm using a Sony ZV-1 and it's worked out pretty well.
Those cost more. It doesn’t make sense to spend more than needed on something you’re only going to use as a webcam. Webcams don’t have to spend on holdability or physical durability or any viewfinding.
I also dual call into many meetings. For these, I use my phone to see how my screen sharing is working. I have to do a lot of screen sharing presentations to present data (tables, figures, etc). With this use-case, it’s very helpful to have a second login to be able to see what everyone else is.
Or I’m in a group meeting and I see a text or even a phone call I want to quickly respond to. Apple’s demo at WWDC seems interesting but not sure how much I would actually use it unless it was to partially repurpose an old phone.
As for cameras, I got things setup with my Canon 5Diii but it was way too much trouble to use given even pre-recorded Biddeford is most of the way there with a Logitech C920–and I’m better than most of the people recording videos.