Because there's a bunch of interesting stuff to do, especially for kids, and you can do a lot of it without breaking the bank. The zoo, the Arch, Grant's Farm, City Museum, Science Center, Magic House, Botanical Gardens and the brewery tour are all pretty centrally located and not terribly expensive. Just because they aren't things you'd be interested in doesn't mean they're not pretty fun things to do on a family vacation. And quit making me defend St. Louis, it makes me feel dirty.