Our civvy maintainers at Sheppard wear a dark blue uniform that sorta looks like a cross between the old style olive drab utilities and a more modern cut "maintenance" style work outfit. It has built-in creases where there should be creases, looks like it's wash and wear, and it looks fairly decent. The Calif Hwy Patrol officers at vehicle inspection stations wear something similiar, and they look fine too.
But if you give mx troops their own uniform, then EVERYONE would want their own uniform. Heck, just look at the trouble pilots get into for having our own uniform. Everyone hates us just because we get to wear nice comfy flight suits

Even missile and space types had to switch away from their special uniforms, and of course they switched to... flight suits.