The Main reason you want to use debt is to increase your return...

The Main reason you want to use debt is to increase your return on equity.

For example if your company's assets are earning 20%, and you have funded them with 100% of your own equity, you earn 20% on your investment.

However, if you can borrow money at 5% and you use it to fund 50% of the project, then because you only have to pay the debt holder 5%, you keep the additional 15% their money is earning for yourself, raising the return on your equity to 35% instead of the 20% you would have gotten if you funded the project yourself.

However this adds risk, and in FMG's case, reducing the debt has been a good thing, but yeah as the debt pile shrinks and the interest rate reduces, Buy backs or acquisition will be more beneficial.