A few swap meets I use to go to all the time seemed to have suffered the same fate others mentioned. Back in the 80’s I would go to the swap meet/car shows that had plenty of good part vendors as well as memoriabilia like manuals, brochures, etc. Enjoyed spending an afternoon and getting a deal now and then.
When I moved to AZ, Tucson had the indoor and outdoor swap meets that were really good. They still might be going on but I have not been to them in over 15 years. I could get the car magazines I liked a few days before they were in the stores, comics for my nephew, and some car toys I liked. There were decent items with plenty of vendors. Then with Ebay and such getting bigger around 97-98, the good vendors headed online. Within a few months the tables were now loaded with cheap sunglasses, plastic containers, “as seen on tv” type junk was taking over. Eventually less and less vendors were displaying and it was not worth the trip.
I do remember one of the vendors I was friendly with just decided going on Ebay was easier. He did not have to cart his stuff all over, packing and unpacking, setting up. He just felt it was better for him running his business from home and becoming a mail shipping setup. He did go to few car shows, but never to the weekly local swap meet.