This isn’t related to modern society, necessarily. The US total fertility rate was well over 3.0 in the 1960s, but even then most women worked outside the home. It’s also not necessarily preference. The average number of children women say they want is 2.7, while the fertility rate is now well under 2.0. I strongly suspect it’s the result of the sexual revolution in the 1960s and 1970s, which made it socially acceptable for men not to commit to raising families.
[1] This is actually a fairly new phenomenon, appearing in the last few decades.