1. If no one is allowed to vote, and democracy is an organized overthrow of the government, then the people who are unhappy have only violent means for change and that we don't want.
2. If no one cares to vote but the vote matters, then the few who DO vote has disproportionate power compared to everyone else.
3. If no one cares to vote, we risk an aristocracy where power is passed to family and maybe friends of those in power. We already see that in too many elections where Liz Cheney won her father's seat in Congress based on name recognition, Hillary Clinton riding on Bill's reputation for politics herself, Jeb Bush, Ted Kennedy's offspring trying but failing.