My bet: in some countries because there are many more parents and grandparents. Young people don't have enough votes. A sci-fi like proposal to fix that: people's vote weights 10 at 18 and lose one every ten years. Totally against the principles of our democracies but more forward looking. And very risky for the elders, which are also the most defenseless against changes. I'm not really sure I'd like it.<p>A minor cause: most young people don't think about politics. They have other priorities. This starts a negative feedback loop together with declining birth rates.