A random example would be that there's a huge difference between an 18 year old kid and a 25 year old who has been working, going to school and managing his/her life. An 18 year old is bound to make voting decisions without any real context grounded in having lived a little. They are naive and tend to be innocently dumb. There are exceptions, of course, but I have trouble calling an 18 year old an "adult" other than under the legal definition.
