Because TVs are landscape. These videos are shown at club events.
You showed your colours when you assumed that portrait video is of lower quality.
I never said it’s lower quality. Not once.
Technology to detect whether your webpage is being viewed landscape has existed for a long time, and takes very simple calculations indeed or just a splash or two of css to maximise the video size for whatever screen it’s being viewed on. It’s design laziness and wasted bandwidth to put the silly blurry bars or even black bars down the side of the video. But don’t force landscape on everyone. Smart phones aren’t new and they aren’t going away.