There are historical reasons for all the common aspect ratios, and all are because of physical film formats. Home video presentation was never a consideration i any of the aspect ratio choices for filming movies.
A 21:9 screen really is the best way to handle home video, because it makes the ultra-widescreen formats wider instead of shorter, which was the reason those movies were filmed that way…to feel more expansive. The problem is that without a projector and side masking curtains, showing 1.85:1 movies and HDTV just looks wrong.
Also, a flat panel 21:9 TV that is tall enough to give you the picture size you want is much wider than a standard 16:9 TV. If you have the room for such a wide TV, most people just get a 16:9 TV that gives you a much taller picture on most content. This ruins the effect of “ultra-widescreen” being wider, but people live with it. Then, too, a 21:9 TV would have to be 2520x1080 pixels to allow full 1920x1080 in the center area. That’s creeping up into 4K pixel range, so the TV would be a lot more expensive for just “HD” resolution.