Because it is very hard to find new hardware to test it, let alone expect your users to take advantage of it on their machines. AVX512 is such a mess that Inte

Because it is very hard to find new hardware to test it, let alone expect your users to take advantage of it on their machines. AVX512 is such a mess that Intel just removed it after a generation or two. And on ARM SVE side it is even worse. There is already SVE2, but good luck finding even a SVE enabled machine. Apple does not support it on their Apple Silicon™ (only SME), Snapdragon does not support it even on their latest 8 Elite. 8 Elite Gen 2 is supposed to come with it. Only Mediatek and Neoverse chips support them. So finding one machine to develop and test such code can be a little difficult.