Reason A: If teens are allowed to get jobs at 15 or 16 and then have to pay taxes on their income, then they should be allowed to vote at a younger age. They are contributing to society so therefore they should have a say.
Reason B: Responsibility. From an early age it is important to instill responsibility into children. Knowing how the government works from an early age can help young people make a difference in their community and in future politics. Every generation is the future of America and they should have a say in what will happen in their future.
Reason C: it might force teens to be more proactive and observant of things that are happening around them. Teens tend to be self centered but by lowering the age, teens would be forced to get involved in politics and act like citizens instead of like spoiled brats. They might also be able to volunteer and help politicians see issues from their point of view. Some teens get interesting in politics or other issues from an early age because of situations they might experience at that young age.
Hopefully this helped and good luck.