I thought it was clear from context that I was referring to people who want to have kids with a romantic partner (I suppose for fertility rate purposes it doesn't even necessarily need to be with just one romantic partner, or within a monogamous relationship).

Lots of people don't want kids these days relative to 50 years ago, but even among those who do, they're delaying the process, often to the point where it becomes less ideal due to age. Many people who wanted kids when they were younger end up not having them as a result (and many who want them haven't had them yet).

Having a partner (or partners) to do it with is a significant factor for many, among other factors like concerns about affording food and housing for oneself, let alone for additional dependants.