“Since marriage is a partnership, I’d like to know who I am and what I’m able to offer financially and how stable I am, before I’m committed legally to someone,” Ms. Simson said. “My mom says I’m removing all the romance from the equation, but I know there’s more to marriage than just love. If it’s just love, I’m not sure it would work.”

Sociologists, psychologists and other experts who study relationships say that this practical no-nonsense attitude toward marriage has become more the norm as women have piled into the work force in recent decades. During that time, the median age of marriage has risen to 29.5 for men and 27.4 for women in 2017, up from 23 for men and 20.8 for women in 1970.

Both men and women now tend to want to advance their careers before settling down. Many are carrying student debt and worry about the high cost of housing.

They often say they would like to be married before starting a family, but some express ambivalence about having children. Most important, experts say, they want a strong foundation for marriage so they can get it right — and avoid divorce.

“People are not postponing marriage because they care about marriage less, but because they care about marriage more,” said Benjamin Karney, a professor of social psychology at the University of California, Los Angeles.

Andrew Cherlin, a sociologist at Johns Hopkins, calls these “capstone marriages.” “The capstone is the last brick you put in place to build an arch,” Dr. Cherlin said. “Marriage used to be the first step into adulthood. Now it is often the last.

“For many couples, marriage is something you do when you have the whole rest of your personal life in order. Then you bring family and friends together to celebrate.”