I dunno, I think it's a fair question.
My take - I don't think it's due to the history of HEAVEN (and this thread wasn't meant as having a go at HEAVEN) nor to the whingers/gunnas/not doers.
Victoria has several vintage clubs who hold regular race meetings all over the central/southern part of the state. You could be assured of a ride most months at one of these clubs and there's a good chance that a race will be on near your home. Qld is similar in that it has two clubs in the SE with several tracks from the Sunshine Coast to the border. Again, there's a good chance there's a race near you. Even Coles Creek, 1.5 hours drive from Brisbane, has the benefit of being slap bang in the middle of an area that was a real part of the dirtbike scene in the 70s/80s. I'll bet you that the demographic of riders at a Coles Creek round is different to a Tambourine round.
NSW however has only a couple of tracks in regular use - Canberra and Bulahdelah. We do have Clarence too. Canberra and Clarence are modern tracks and I think that doesn't help. I know I am not that keen on riding my 75 RM125 around those tracks. I can do it, and I have fun, but I do look longingly at the photos from VCM, QVMX and BMCC.
Equally, these couple of tracks aren't really well situated. Bulahdelah is a long drive for south coast, Canberra or Snowy Mountains area riders. Canberra is better for those, but then it's a fair haul for Sydney and north coast riders.
I know some of those events are two days, but I am not sure that really helps as it's not always easy for people to get two days off regularly to go to a dirtbike race. I can barely do that for an event here in Canberra.
So, my opinion? Tracks too far away from the majority of riders, tracks that don't suit the majority of riders. I reckon that if a club held a good natural terrain grasstrack twice a year at a track within 1.5 hours of Sydney on either the Canberra or South Coast side, made it a one day event on a Sunday, and guaranteed the riders plenty of rides, and then got out there and promoted it, you'd get a lot more turn up. I wonder how a vintage event at Coopers Gully would go, for example.
As for HEAVEN, to some extent I think that 60-70 riders might be about it for now. I would like to see a greater effort to promote HEAVEN as a club - to that extent a more personal touch on the website, more regular website updates and maybe a newsletter would all help. But I am conscious it's hard to find people to do those things.
PS: By the way, I just thought I'd go on record and say that having ridden vintage events in both Qld and NSW, and also having attended several Classic Dirts, I think the HEAVEN events are as good as any, so I don't think Dennis need feel that this thread is knocking all the great work put in by the club. Magoo's question was more about what is needed to get more riders to whatever vintage events are on around this way.