It's not like everyone married and had children in previous times. If we look at Western Europe in medieval times, if you didn't feel a vocation for family life you had a vocation for religious life. Monks and nuns didn't have kids, they basically devoted their lives to the "work" of being a monastic. In upper class families with 3 sons, one inherited, one went to the military, and one went to the clergy. And older people also sometimes went into a religious community as a form of retirement.
Also, I read once somewhere that except for the nobility, people generally didn't get married young. Men needed to be well enough established to support a family (a farm, a trade) and women had to amass a dowry.* If I remember correctly men were marrying in their late 20s to 30s and women were marrying in their mid twenties.
And even in more recent times there were people who didn't marry - they were the youngest child and looked after their aging parents, or the oldest son stayed to work on the farm and inherit it, or whatever. Look at Anne of Green Gables, and Matthew and Marilla Cuthbert.
This marry and have children early and often is a product of the late 40s and 50s, after WWII.
https://www.statista.com/statistics/1037156/crude-birth-rate-us-1800-2020/ Otherwise the birthrate has been steadily dropping since 1800 - as child mortality decreased the push to have several children in the hope that a few would survive lessened.
*As someone who took up the fibre arts in retirement, and has found out just how much time and work goes into making fabric without industrial age equipment, I can understand that it would take years to amass the linens needed for a household. Remember that for Vikings to go viking in their longships, they needed boats that had sails. More resources/time/labour went into making the sails than making the boat.