Care to explain? I can make assumptions but I will probably not have the same interpretation you have.
I mean, I'm in my 50s and I'd be out in the streets throwing down with the cops if they took away the right to vote from a significant portion of the population.
At 18 most people have too much going on (high school graduation coming up, studying for and applying to college and/or looking into employment, potentially seeking housing if their parents are kicking them out, etc) to have much capacity for political participation. That picture is significantly different just a couple of years earlier, where time and mental bandwidth is generally at more of a surplus, and so if people became capable of voting at that age it stands to reason that more would take advantage of it (and continue to after that).
Denying the vote to a thoughtful 16 year old is worse than giving the vote to a 29 year old that takes it for granted. And then same thing applies to a 2 year old, if they can independently mark the ballot...