Contrary combinations

Why is it that I cannot seem to manage to consistently compel my children to the dinner table on time, but the moment I sit down in the bathroom or try to make a phone call, they arrive with bells on from the far corners of the house or yard?

If only I could think of a proper way to combine these three activities without repulsing myself, breaking all manner of collectively accepted rules of proper sanitary food handling, or involving the person on the other end of the phone in an elaborate Pavlovian scheme.