You're missing the obvious answer, it's a zero sum game. If a company pays top of market, they can absolutely find enough qualified candidates any way they wis

You're missing the obvious answer, it's a zero sum game. If a company pays top of market, they can absolutely find enough qualified candidates any way they wish to subdivide them (by race/gender/background etc). The rest of the companies won't be able to however, and now they look bad so they either have to (possibly) lower their standards or have bad PR.