Socially, we're programmed to believe all women want to be mothers. If we don't, it is then assumed there is something wrong with us OR we will change our minds. We are never taken seriously when we say we don't want to be mothers (or in some cases wives either). I know from decades of personal experience. Our society bestows a value on women who are wives and mothers and judges those who aren't. Happy being single? Don't tell people. They will tell you you are lying to yourself. Tell them you don't want to have kids when they ask, and they will trip over themselves to tell you why you are wrong.
While biologically we can have children, doesn't mean we all should have or want children. There are plenty of guys in the world who don't want to have kids, but less often they get the same level of shame or judgment women who elect to be child-free do.
Motherhood is one of many life paths. So is marriage. Some of us elect not to walk either of these paths. And boy, we get a lot of flack and pity for it. Look, my choice not to get married and not to have kids is not a dig against those who want that. Blessed be - go off and be happy. My life and my life choice isn't an affront or statement about your life choice. We're just doing different things with our lives. Neither one is better or worse.
I never had the urge to be a biological mother. I like kids fine, contrary to what many people think about child-free people.
People only just stopped asking me when I'm going to have kids 1. because I'm over 40 and 2. because I'm dating someone who has his own children from a previous marriage. And 3. Now it is assumed I just couldn't have them so people mind their own business a little more and don't ask for fear of an awkward discussion that, frankly, isn't any of their business anyway.