It's not square. It's usually cut in 4:3 format.

The imaging sensor is a rectangle in roughly the same aspect ratio as what is captured by the stills mode.

You can see that in any teardown.

I do agree there's no "right orientation" though since it's subjective. However having a square sensor would be illogical

Yes you are holding it wrong because the resulting video is clearly wrong if you view the video on a TV (same aspect ratio, other orientation), a computer or if you watch movies, or if you, well, see out your eyes. If you want to capture just about any action, it's going to look better in landscape, and that is why EVERYTHING until phones were put in the hands of plebs is shot in landscape.

Now, you could argue that we've gone more mobile, and newer social media formats expect portrait, but, that doesn't change that it's risen because people take videos and never consider, "hmmm, if I turn it around, I get a better picture and it looks more like a TV! Duurrr." Just because it's more popular doesn't mean it's not stupid AF.

I know plenty of people that don't own a TV or a monitor, they only own a phone and they have a locked to portrait mode. I wouldn't be surprised if you checked the world and there were more of those people than TV owners at this point. Why should they have to make their videos for TV users?

Point-by-point: phones can (should be able to) unlock from portrait for video. As I said, video is generally better in landscape, so it's not really about TVs, TVs are landscape because viewing video is better in landscape. Why anyone has to even argue this OBVIOUS point just demonstrates the militant ridiculousness of people that get on the defensive because they often (not always) put no thought into their video compositions. Vertical video look stupid, get over it.

What if I record videos for viewing on phones? Do I deserve insults too?

Well you can do what ya like, but I, as a viewer do have the ability to turn my phone to landscape to view landscape videos. What are you shooting? Pile drivers in action?

“Talking head” video is better in vertical orientation for the same reason painters have been creating portraits in vertical orientation for centuries: humans are vertical. Much of TikTok and other networks’ vertical stories are indeed videos of people.