Compiling with -march=native makes for brittle binaries, since the binary might contain instructions that are not be available on slightly older CPUs or on virt

Compiling with -march=native makes for brittle binaries, since the binary might contain instructions that are not be available on slightly older CPUs or on virtual machines. So it's only suitable for software that's performance sensitive but won't be distributed to other machines (or at least won't be distributed outside of a strictly controlled environment). It wouldn't make for a good default.