For myself, because I have raised children of my own. I have 5 kids, 2 boys and 3 girls. At 2 years old, kids do not give a flying fuck about social norms. They just want to play. And from the earliest ages you see children playing differently based on gender. You give a small child the choice between a doll and a stick, you can guess which will be picked by gender and be right most of the time. Give your daughter a dump truck and she will turn it into a stroller. Give your son a doll and he will be wrestling with it.