"This RFC is proposing adding an x86_64_v3 port in Arch Linux. Assuming SSE4 and AVX2 (and others) while compiling will provide greater out-of-the-box performance in Arch Linux. There are also implications in terms of battery life for laptop users."
"Providing all four architectures would require a lot of resources in terms of build time, and mirror space. Providing x86-64 and x86-64-v3 only is a trade-off in gaining support for more optimised binary support for new hardware (while not requiring the absolute latest) and additional build time and storage associated with providing multiple architectures."