I have never been to the Paducah Quilt Show but hope to maybe next year. I think it is so successful because the community is so involved. There is transportation to and from many locations to the convention center. Different organizations offer meals so it is easy to find a place to eat outside of the center. And it's held in spring time!
There seems to be so much to see and do in Paducah which is what makes it so successful, it seems. Other shows just don't have this and may be why people don't want to invest the time and money to attend and why vendors don't see the sales to make it worth their time and money.