This. I am completely aware of the problem of vertical videos, but constantly take them out of wrist/grip convenience.
I'm baffled as to why iPhone/Android doesn't offer a feature that allows you to toggle horizontal video from a vertical phone. I feel like that'd make 50% of smartphone videos infinitely more watchable.
Having a square sensor or a sensor rotating physically is a big tradeoff in cost or complexity. Until now no one cared to make these tradeoffs for large scale selling cameras, and the few attempts to fill the niche didn't seem to be so successful. I think in the photo world it's the same niche level as for true B&W sensors.
And even if you do hold it horizontally, you won't manage to shoot a perfectly aligned shot easily by yourself. For example, if you try to get a shot of a sunset.