Most investors are ordinary hard working Australians. Most investors are just trying to have something for their retirement because there is no way their super or the age pension will sustain their lives, given current life expectancy (which will increase over time as well) and the rising cost of living.
I had a look at 2014 statistics from ATO (because I'm a huge geek) and found that the majority of people in high income brackets (above 80k) had, on average, extremely low rental losses. Those on incomes of 200k-500k (adjusted taxable income, I.e. Adding back the losses to their taxable income) were reporting losses of about $700-$1000 on average. That's a saving of tax per investor of around $500 max. Meanwhile, there was an overwhelming number of investors in low income brackets (again, adjusted taxable income - so you can't argue that their income was low "because of negative gearing"). The rental losses claimed were between $5000-$20,000. Some of these people had almost no income from wages or other sources. In other words, they didn't save any tax from negative gearing. They are probably the same people who are on a pension. Most of them though were just ordinary people on average incomes. This is where most of the negative gearing is costing "Australia" tax revenue.