Came home last night to see a young woman from down the street bringing her 2-3 year old daughter up on the front porch of my house to see my downstairs neighbor. They talked to my neighbor for a minute while I got my stuff together to get out of the car and go up to my own front door (on the same porch) and then they went to leave. The girl seemed disappointed and didn't want to go.
The mother said, "Honey, they are playing an xBox in there and that's not somethings that girls play with, that's a boy thing."
I suspect it's partly one of the made-up excuses on the spot that parents say to get their kids to comply when they need them to go along with the current plan, but at the same time the words were very very clear in labeling a gender-neutral activity that the girl obviously wanted to play as belonging to a particular gender... and the same reasoning probably gets provided in other circumstances as well.