[scotcha1]

a rear camera would not be useful at all for an on-screen walkthrough as it would be facing a wall or a surface. my face on the other hand, added for a personal effect, to an on-screen recording or so you can easily match my voice and my mouth to better understand me. perhaps you haven't seen a face + full screen desktop walkthrough? https://www.getcloudapp.com/. very useful.

a facetime call with my wife does require video, because it's a facetime call. i want to see her.

my kids school remote calls do require video because their teachers require video on. they do this because kids from ages 6-18 may not actually be paying attention in class, so the hardware camera is used to help the teacher.

if you were to look on youtube for walkthroughs of products, or twitch streams, you'll frequently see front facing cameras added to videos because people do actually like, enjoy, and find value (you can follow along to voice/face/emotion) in them