Interesting topic and I guess I can add my two cents as well.
Autocross was the best thing ever when I was in college. The local SCCA region was full of welcoming people, the primary venue was 20 minutes south of campus, and I had a NA Miata that came to me bone-stock, so I did a few cheap things to it and had it planted square in STR. Events were well-attended and I could afford the $30 or so entry fee. Great way, as a college kid, to spend my Sunday and improve my driving.
After graduation, I tried a few events with the DC-region SCCA. The events felt overcrowded and nobody was really that friendly. I had to travel farther (an hour at minimum) to attend. At this time, I was starting to work for NASA more as well, at their road course events. I was using the credits I earned to start weekends of HPDE. I realized that I'd rather drive an hour or three to spend the whole weekend "playing cars" on a real racetrack, instead of driving an hour or so to stand around a hot asphalt parking lot for three or four minutes of driving around cones.
The impression that the younger crowd gets from SCCA, based on my discussion with some friends, is that it's older age-wise and not as welcoming as NASA or these smaller groups like CDC. Gridlife has been a nice way to appeal to the younger crowd more recently, although I think they have more to offer for HPDE/entertainment compared to competition.
There have been recent "Trackcross" events held at Dominion Raceway and Summit Point, which are autocross-format (best time achieved) but using a section of a real track. Those have gone over very well, and appeal to more people vs just a parking lot. Granted, racetracks aren't as accessible location-wise to everyone, but the approach has been successful regardless.
And speaking of competition, the SCCA autocross rulebook/classification procedure is bananas. I've been competing in various form for what, 11 years now, and still am not entirely sure where my racecar fits for the sake of a casual one-off autocross with my college region.
I'm not knocking autocross, it's a great way to get people hooked on motorsport at a cheap and fairly risk-free level -- and nearly any car can be used. But, the value prop just isn't there for a lot of us, particularly not with the SCCA.
