Second, look at the employment rate charted over the last forty years or so. Some of that may be explained by retiring baby boomers, but it's the following generations that will need to pick up the economic slack to pay for retirement, healthcare, prop up their home values so they can retire, etc.
So you are agreeing - since before one person was devoted full time to homemaking, and now they must find paid employment - that work still needs to be done so it must be done in addition to the hours worked at an employer.
so instead of one person doing 40 hours at an employer and one person staying home to keep up the house - we have two people working 40 hours each and then working overtime to maintain their house after work. We've added 40 hours of work to the equation.