Is the situation such, that there is so many other things to do that are much less expensive than classic racing and as has been pointed out on previous occasions, the cars are now so rare and expensive to buy (and repair) that they tend to sit locked away in sheds.
As I see it many motorsport events are put on for competitors not spectators and therefore do not generate vast gate takings.
We are not the only sport that has problems attracting spectators. As an example look at the crowds (or lack of) at both rugby and cricket matches these days.
There is also the situation where there so many other family-related activities such as fishing, boating and mountain biking that have had the effect of taking our base of hardened fans away from the sport.
I always enjoyed going to Pukekoe but as Ray has pointed out viewing became more difficult with all the safety fences etc that it was easier to stay home where the food was cheaper and the toilets closer and watch on TV.