i hear this a lot and i also feel like this population is declining very significantly for a lot of reasons (cars that people care about are unaffordable, most cars on the road tend to fit into one of a very small number of categories, people find other ways to navigate depending on where they live, people don't do as many activities out of the home that require a vehicle, etc). at what point does the real population of car enthusiasts become small enough to be irrelevant in public policy and infrastructure decisions?
My guess is that they are more successful at suppressing subdomains than at getting them indexed. After all, they are not in control of what search engines do, they can only send signals.
For reference, I have a simple community event site on bearblog.dev which has been up for months and is not in any search index.