I haven't been to Lancaster in a number of years. I have not been to the NJ Quilt Fest in a few years either but did notice the last time I was there the reduced number of vendors.
While the quilts at any show are always spectacular, I think many of attend shows to also see new products; methods; etc.
I imagine the cost for vendors to participate has increased significantly in the last several years. As others have said, with many brick & mortar stores closing and only doing online, this changes the landscape, I'm sure, for show organizers as well. The fewer vendors available, the greater the individual participant cost thus driving down the number of participants. It's a downward spiral waiting to happen, unfortunately.
My observation at the last NJ Quilt Fest I attended...many, many longarm vendors and demonstrators. Very few vendors selling fabric; tools; etc. I'm not in the market for a long arm machine but I can almost always be sucked into a few tools from other vendors.