It's called the "Free Market". The Free Market has determined that it now requires TWO incomes to raise a family. Enough working spouses over time raised the standard of living enough where the Market and Businesses saw prices and services could be increased based on the Market.
If you don't like it, too bad. Conservatives whine and scream about the "Free Market" and "Capitalism", and this is the PERFECT example. Waaaah, my wife has to work but would rather stay home. Well, why don't you take Conservatives advice and "innovate" and use that "rugged individualism" and get a second job?