The capitalists speculate on the two following factors: the female worker must be paid as poorly as possible and the competition of female labour must be employed to lower the wages of male workers as much as possible.
Most arguments for instituting or raising a minimum wage are based on fairness and redistribution. Even if workers are getting a competitive wage, many of us are deeply disturbed that some hard-working families still have very little.
Believe it or not, we will actually be better and happier workers if we are allowed to be better parents. We might even rediscover our capacity for fun.