I’m not as familiar with the NEON side, but AVX512 support is pretty variable on new processors. Alder Lake omits it entirely. So we’re still in a world where AVX2 is the lowest common denominator for a system library that wants wide support.
Case in point: I've been very disappointed lately when I wanted to try Ghostty on my laptop and the binary compiled for Debian failed to run due to an invalid instruction. I don't want to force the same experience to others.