maybe it all comes down to why people join PCA in the first place... some do it b/c they want to meet other people w/ similar cars/interests/hobbies
some do it b/c their friends joined, so they do the same
some do it b/c the dealer told them so
(made them aware of it b/c they never knew about PCA)
personally, I do it for track access. I could get plenty of tracktime w/ several different organizations, but it wouldn't be as convenient, and I'd see different people within different clubs, and never really get to know them. That *could* change if other local Porsche owners signed up for the other clubs' events, but right now I don't have to go through that. It's because PCA makes so convenient, accessible, and (semi-)affordable. I don't need to hunt down different clubs, compare and contrast their track schedules etc. PCA makes it easy, for which my lazy butt is grateful. I even get email notices about track time. Can't beat that.
That's what I get out of PCA. It's enough for me so I don't have a need to be involved w/ the club in some other way. Getting on track takes good planning and organization so it's beneficial to go thorugh PCA, but if I want to attend a barbecue, I can do that w/o an organization.