As for the absence of carbines, 03's and revolvers - it is not a story that they are unwanted. They are wanted and kept off the sale tables because the owners appreciate them. I attended an estate auction recently and found these described firearms were fought for during the sale.
I used to visit every gun show within driving distance from my town. Often times my attendance was to visit with long time friends. As this number of friends got lower my interest declined. The increase in plastic firearms, t-shirts and non-related materials, and the absence of traditional blued steel / walnut long guns has caused my attendance level to one show every other year, if even that often. Online sales have replaced the shows, but that is not a bad thing. Makes it easier (or even possible) to find that one specific item you would not even find at a walk-in show.