* Not interested.
* Not competent enough to make a decision.
* Social isolation.
* Frustration.
* Some participate in other ways than voting.
Some other interesting facts from 2015 [3]:
* 30% turnout of young people between 18 and 30 years.
* 67% turnout of old people between 65 and 74 years.
* 53% of men participate, 46% of women participate.
* Old women do participate less than young women, possibly because Switzerland introduced votes for women very late in 1971.
* The concordance system [4] leads to less fluctuations in the composition of the government. It's not like in the US, where you have only 2 completely different parties fighting each other. So, less changes, less reasons to go to vote.
* Many people are happy with the status quo. Another reason to skip voting.
[1] https://www.aargauerzeitung.ch/schweiz/warum-die-mehrheit-sc...
[2] https://www.beobachter.ch/politik/wahlen-2019/wahlen-2019-wi...
[3] https://www.nzz.ch/schweiz/eidgenoessische-wahlen-2019/wahle...