In a lot of movies that take place in the future there's two classes of people, citizens and everyone else. To become a Citizen you typically have to contribute something to society (e.g., enlist in the military to fight against aliens, devote your life to civil service, pay taxes, etc.). If you don't want to do whatever is required to be a citizen, no biggie, you just don't get to vote.
I used to think it was just an interesting, common, predictable sci fi thingy. Now I look at how stupid and useless many of the people are who vote, and how they rough ridin' register bums to vote and then absentee vote them, and it doesn't seem so far fetched.
If you contribute nothing to society, why should you get to vote? Why is it a birthright instead of something earned? I think if it had value it would have importance, and we wouldn't be in the predicament we're in today.