So you have a problem with portrait stills too? Actually, I know we're not there yet and I'm sure most agree with you generally and especially with most subjects captured, and I know most vertical video was likely done without thinking through display (like my daughters first steps video ), but it wouldn't be technically hard to make the same adjustments as stills for one-offs or width locked online players (though I think I've seen probably only five in the last decade), no matter monitor ratios and our eyes horizontal placement. Again if there's a value in stills composition which wins over strick template layout, why not video... at least occasionally? Can you tell I just had this argument with a co-worker?
It's actually the opposite solution. As the videos were captured at 1080x1920 (iPhone 5 vertical), one of the 4K widescreen standards of 4096x2048 allowed a minimum of upsampling (1920 v. 2048) with obviously a ton of left/right letterboxing during editing. And yes, that's when we had the argument. His exact repeated phrase "Video is video!"