Isn't this because its an inherently expensive and wasteful sport? (As in the sheer cost of parts, engines and components that only last a couple of runs etc)
I know of one top fuel team who is always begging for money on Facebook and attempting to to get crowdfunding etc, for what is essentially one man's hobby, and whilst having corporate sponsorship
I know the spectacle is awesome as I've seen one before, but the fact of the matter is that drag racing is a niche spectator sport in Australia, hence the lack of sponsorship dollars, it could well be a case that it is simply too expensive to run these top level classes if the teams cannot finance themselves (given that every run down the strip costs $20k apparently)