What would be the charitable purpose of sharing stickers with strangers? What is the noble purpose of the sticker? When playing Monopoly, are you going to give away your properties, hotels, and houses to some unseen person in the next room? Hell, no! Does that mean you are a bad Christian?
Ask the kids to share some of their meal with a starving child in the next room and let’s see how many are willing!
Well, exactly. The tested action is meaningless. Even if it was meaningful, like sharing a meal, you don’t know what people would actually do - vs. what they say they’d do - unless you observe them doing it in real life.