Women that marry in their late 20s and have kids in their 30s aren't really thrilled with their dating prospects when they're fast approaching 40 and have a kid.
Men that marry in their late 20s and have kids in their 30s don't like the idea of living in a crappy apartment, driving a 15yo Civic and eating rice and beans well into their 50s because they're getting bent over for child support.
If you get married and feel you've made the wrong choice later in life you have more motivation to "make it work" because your ability to "do better" is worse.
50yr ago it wasn't uncommon for people to get married in their early 20s and be divorced (with or without kids, usually with) by 30. Millennials may just have skipped that phase.
Edit: Never mind that last paragraph, it is contradicted by one of the graphs.