My DSLR camera has 14 bits. Having a high dynamic range is useful in capturing a scene with both bright and dark elements. The new 4K-HDR TVs have more pixels, but they also have 10 to 12 bits of color depth (versus 8 for standard HDTV).
Humans can only distinguish about 30 shades of gray, so 256 is way more than anybody needs, unless you’re doing scientific research.
https://www.popsci.com/humans-can-only-distinguish-between-about-30-shades-gray