Why is super required by law?

The Australian government, like governments in comparable countries, is moving away from the notion that retired people should live on taxpayer-funded pensions. Requiring all working Australians to have their own retirement savings plan places the responsibility on the individual rather than the community as a whole. Employers are required to pay 9% of the eligible employee’s salary into a complying super fund, such as EquitySuper fund and its products, EquitySuper Investment Engine and EquitySuper Super Focus.

source: http://www.eqt.com.au/superannuation/personal-super/frequently-asked-questions.aspx#1