I have no personal insights here, just speculation.

As to why there were no guys getting tickled, maybe Don was able to get the girls to perform because there were not guys around (other than Don). And maybe he didn't want to cross the line into porn, though he did eventually get one or two videos where the girls were at least partially undressed.

There has to be an amazing story about how Don managed to find and video all those long-haired girls. And then what happened to everything. Why'd they go out of business? Was it just a hobby for him?