why do you think people want or have kids?

Biologically it is simply the natural reproductive drive. All sexually-reproductive animal species have their own versions of this, and ours is no exception.

Socially, many people do want to create their own children, even one day to become grandparents, for future company, care or lineage reasons.

It's a biological drive that manifests more strongly among some than others.

To create, recreate and procreate.

To pass on a bunch of stuff to.

People want to have children so their lineage can continue through future generations.