Birth tourism
Some countries do not allow their citizens to renounce their citizenship or only if the citizenship was acquired by birth there to non-citizen parents. In Argentina, Brazil, Ecuador, Peru, and Uruguay, voting is compulsory for citizens. In Bolivia, Brazil, Chile, Colombia, Cuba, Guatemala, Paraguay, and Venezuela, military service is mandatory.
Donkey vote
In systems where voting is not compulsory, it seems counter-intuitive that many who attend the polls would be apathetic. However, there may be countervailing factors that produce a "donkey vote" even with voluntary turnout. In many US elections, a voter may well be intensely interested in (e.g.) the Presidential contest but not in other, less prominent races on the same "long ballot".