As TN3135 clearly explains the limitations apple puts on the low level networking, it doesn’t really give a reason. Presumably the power consumption problem. But as the battery technology continues evolving, it could be exciting that apple might loose the restrictions someday. The watch itself is powerful enough to do a lot of sophisticated works, sure it works best with companion apps on iPhone, but even as a standalone device, we can still provide many advanced user experience with low level networking supports.
wish apple guys can read it and give a consideration.