I constantly do this when navigating large files. Zoom out for context (better than a minimap), zoom in for detail. I use the trackpad for it though, not ctrl/cmd-+. I also do it constantly in web browsers, and am consistently amazed by the way that minor changes to font sizes break the layout of any website that has had a designer near it.

You use them in pair programming, when you peer sit a little bit further

I often use it when sharing my screen. I like the feature quite a lot.

Live coding during a presentation or on stream is another use case in addition to the sibling comments.

Well it seems quite expected doesn't it. Different people and groups of people have different customization needs. I change my font size if I sit back or in a different position or use my standing desks.