1) Some people are under more stress than others, and are less able to summon the effort to vote. Admittedly, this does also include people in rather different circumstances, such as elderly homeowners who become unwell at election time (especially after the postal vote deadline).

2) Voting arrangements aren't uniform between countries (or even within one country), and travelling some distance to a polling station and then queuing to vote is a burden some voters might experience much more than others.