Capital is usually what makes human labor more productive; we aren't getting smarter, faster, or stronger.

For example, if you work in IT you benefit from massive capital investments that researched, developed, and deployed every bit of technology you use, from 18th century research on electricity (and probably earlier research) to every component in your PC to C to the Internet to AI, to the technology used in the global supply chain that makes it all (to much, much more) ... Should you be paid as if you were utilizing no capital, and you were working in a cave by firelight with carbonized wood on the wall?

Almost all of anyone's productivity, I expect, is due to capital investment that they didn't make.