If employers cut their wages, and workers quit, what happens to the wages?  Workers may quit, and are likely to look for another job that pays more.  In fact, that's exactly how the labor market works already.  So employers don't have monoposony power over their employees overall, they have to pay enough that their trained employees won't quit en masse.  We already know that, in general, that market labor rate is higher than the minimum rate anyway.  My daughter was offered over the minimum rate to work at a fast food restaurant without any work experience at all.