Well, I think people usually tip the delivery drivers. They are the ones who had to drive their ass out to the house. And they're usually underpaid because employers see the tip as a compensation for their low wages. (In California, at least, the minimum wage for occupations where tipping is expected-- i.e. pizza delivery man, waiter, etc.-- is MUCH lower than the normal minimum wage. This is simply because they feel that the tips should overcompensate for the difference in hourly wages.)

However, I do think that any tips from pick-up orders should be shared with the chefs, if not given exclusively to the chefs.