LOTS of people. Disney stopped sending out multiple tags per person earlier this year, because most airlines charge for even the first checked bag so most Guests only check one bag per passenger. But did you call the regular Disney number, or did you call the Magical Express toll-free number? If you call the latter, and there's time, they'll send out the extra tags you need.
Otherwise, trust us - many Guests do not tag their luggage for a variety of reason, yet Disney manages to collect and deliver it all. Show your claim checks to the CM at the Welcome Center and someone will be dispatched to pull your luggage and divert it to the sorting center.