You would have tried negative gearing in shares or houses and profited from it. Clearly this is not the case.
You are paying out child support or
You have over committed on a dream house instead of buying a home and living within your means.
or you have a massive gambling problem,
or you have never employed the services of an accountant.
Basically, you're earning a decent living and due to one or a couple of the reasons above, you are paying 40 cents in the dollar and that is more than likely your own fault.