Briefly, near the beginning. But not for the rest of the video.
If you're watching a video on a phone, it's trivial to rotate the phone 90 degrees. On a TV or computer, not so much, so you end up with a ridiculous amount of wasted screen real estate and objectively inferior image resolution.
I found a discussion on the topic here[*]. The consensus seems to be that “wasted” sensor area outside the circle would not be marketable.
https://photo.stackexchange.com/questions/109452/is-there-an...
Suppose you implement horizontal recording while the phone is vertical; this would mean the video preview is now scaled and takes only a fraction of the screen (the same way watching horizontal video on YouTube while in "portrait mode"), which people would find annoying.
Alternatively, you could not scale the video; now the video preview displays only a vertical slice of the frame. It looks OK, but people would soon discover the actual video a screen's worth of image on each side of the preview, leading to anxiety and worry - people would have pay extra attention to not capture things that weren't intended to be on the video; they'd soon look for a way to turn this off.
The unfortunate reality is, it's a social problem partially caused by a technological one. Vertical videos are driven by the phone form-factor and because portraits and selfies actually need to be vertical, and people being people, shooting photos of themselves and other is what they care about the most.
There's far better things to focus false internet collective outrage at.
Contrast with a monitor, where it will at least be viewable vertically, even if it too only fills a portion of the monitor horizontally.
Majority of views certainly come from people whose eyes are horizontally next to each other and therefore whose field of view has a greater extent in the horizontal rather than vertical direction.
Admittedly I don't understand where the vertical recording fad comes from. Personally I take pictures and photos that are almost exclusively horizontal except in rare cases like taking a picture of a very tall building.
1. the people doing the recording being too lazy to rotate their phones, and/or the people doing the recording catering to the lowest common denominator of expecting viewers to be too lazy to rotate their phones;
2. so many "influencer" and related videos these days consisting solely of the narrator's face being right in front of the camera, which makes for vertical being the optimal orientation, due to the human face being taller than it is wide (hence the term "portrait orientation"!).
I also hate it, and I also still shoot almost all my photos and videos in horizontal / landscape orientation. I guess that makes me old.
Nobody expects to have to turn their video camera sideways to capture in the "correct" orientation... but you must on a phone.
When you go yo take a selfie of something other than your face, you just keep the habit.
When I'm sitting, holding vertical feels natural, holding horizontal feels awkward again. I can put my hand on a lap and basically rest in vertical. High risk of dropping it in horizontal (and while rotating). Same for walking.
I don't really see how you can do it "easily" apart from purely geometric considerations. I can rotate my PC display more easily cause it's arm-mounted (which is one of the PC life changers).
where the vertical recording fad comes from
Most popular content today is "person focus". People are vertical.