Some of us do that, but you are correct in that the vast majority seem to have no concept of how to market a product.
Whilst a/c are sitting on the ground they don't make money, a lot of the time however, they won't lose money either, so many wouldn't even think about "special offers" as they think it would lose them money, forgetting that in the long term it would probably help boost sales.
Most flying schools make money despite themselves, not because of any particular marketing genius!