Because they're not. PRC has worst fabs due to equipment sanctions, and now expertise sanctions (first by TW, then US). But said sanctions were placed at all because the cost and quality (east asian work ethic etc) of PRC semi workers weren't in question. Versus US workers being described as "group of giant babies" by TSMC employees ranting on PPT about doing more work for less pay than Americans in Arizona. Experience doesn't matter if you don't work hard enough. It's precisely because PRC workers, who can keep up with TSMC "military" pace, have demonstrated potential to run great fabs that led to companies like TSMC expanding in PRC in the first place, and why US had to do export controls, and do massive CHIPs subsidy to get fabs on US soil.