Sims invading home (Private Dwelling Lot)

This is so annoying. I too have a (supposedly) Private Dwelling and my doors are locked for everyone but the household, yet almost every (in-game) day some bozo waltzes in, laughing and clapping like a seal. Heck, I've even seen people climb in through the window. But because there technically can't be anyone unwanted on my property, Send Away isn't available in their menu. Sometimes they take the trash out, so at least there's that. But I'd still prefer if Private Dwelling and locked doors actually meant something.