People are inexperienced, naive and when you are under 25 you're brain is still developing. 25 is when we are truly adults. This is just a fact.
We have to be aware of the past, the present and the future. They very young are usually only aware about the present.
If an 18 year old is old enough to die for their country they are definitely old enough to vote for the person sending them to do so. Young voters are the most important voters, who gets elected president is gonna impact them the most weather it be a change in tuition, minimum wage, or taxes.