Why are guests making White Cake?

I've noticed this myself. Now, I do have the private dwelling trait on my lot, but that won't stop those who want to give me some useless item. Tina Tinker is notorious when it comes to this. Last time she never even gave me whatever, but started making cake, stopped to play violin (but of course!), followed by occupying my computer. I sent her home eventually, and whatever she intended to give me I will never know. :lol: