The funny thing is that it was the economic policies of Nixon and Reagan/Bush that destroyed the idea of only needing one income to run a family.
LBJ ramped up the Vietnam War in hopes of getting a knockout blow against the Veit Cong. Instead of a fast win he got a quagmire that was gobbling up men and money. Johnson started the inflationary policy of printing money to pay for the War without raising taxes. Nixon ran an an anti-War candidate, then tripled down on LBJ's terrible policy. When the Oil Boycott hit, it made the problem exponentially worse. Housewives started looking for work because Dad's paycheck couldn't cover the costs.
In 1981, when Reagan came in, "middle class" was still defined as one income to run a household of four. In those days, $1 million was a vast fortune. By the time Bush Sr. left office in 1993, middle class was two incomes and $1 million was what a rich guy paid for a party.