There are multiple problems, some of which interrelated. You could go all the way back to the constitution of the USA. The US has non-compulsory voting, becaus

There are multiple problems, some of which interrelated. You could go all the way back to the constitution of the USA. The US has non-compulsory voting, because in theory this ensures only well-informed, conscientious voters turn up. In reality, it leads to pork barrelling. Let's say you are a chicken farmer, in a chicken farming district, and Congress is considering a subsidy (or tax) on chicken farms. You and the boys at the chicken farmer's club have an incentive to mobilize, and try to get people to vote for the party (or candidates) with chicken-friendly views. But the apathetic masses would rather just not vote, because this pork barreling debate will not hurt their wallets that much. Whereas in Australia (which has compulsory voting), a politician who runs an anti-pork campaign can get a fair bit of support from apathetic voters who don't want to be at the polling booth, but have a sneaking suspicion that government spending is not always wise.