Agree that 16 is too young. I do wish, though, that we were consistent across ages for voting, drinking, military service, gun ownership, etc.

Democracy is not based on the wisdom of the voters. It is at it's core, a virtual war. The intent is to avoid civil wars. Yes, we had one, and learned the lesson the hard way of how terrible civil wars are. You count up the bodies on both sides, and if it is close, it is not worth fighting because a war between two even sides is long, ugly and bloody. If it is not close, it is obvious which side would win, so why fight a losing battle. By having frequent elections, it gives us space to adjust and learn. If 18 year olds go off to war, clearly they should be counted in the virtual civil wars we hold regularly.

They can work, but most of them are not self-supporting. 12 year-olds can also work for pay; would you extend the franchise to them too? The current voter base includes far too many fools and ignoramuses; lowering the voting age would exacerbate that problem.

Young children can work in a family business, and before child labor laws even quite young children were working in factories. Generally it was not their choice. The 26th Amendment was approved because 18 year olds were being drafted and sent to war, or volunteering and going to war, yet could not vote, and so had no representation on matters affecting their life and death. As such, it became the defacto age of consent, when contracts etc can be signed. The years from 16 to 18 is a period of significant change in maturity for most people. While it is obvious some are more mature younger than 16, and adults are often less mature, the key thing about being an adult is being 'responsible for the consequences of your choices'. It is not 'earned', it simply is. Having to set an arbitrary age, 18 seemed like a reasonable balance. Setting it at 18 encourages most to finish their high school education, and does not place too great a burden or temptation on younger people.