Answer: Because it should be!
Because we have a somewhat hidden location and did not have a store window (all the windows were glass block), our first challenge was how to entice people to come downstairs and check it out. I scrawled the reassuring words "Come Down...It's Fun" on one of our posters outside. I was happily ignorant that it would be months until we had a "real" sign. Anyway, steadily increasing numbers of brave souls did venture down the vintage stairs and many of them often commented that "Yes, you're right, it is fun!" So the slogan stuck and remains even truer today.