16 makes sense to me. In some states, like SA, it is the minimum age at which you can choose to begin transitioning into the broader adult society. If someone is driving on the same roads as me, working the same hours as me and paying the same tax as me then they should definitely have the right to vote like me too. I don’t think the argument needs to get any more complex or philosophical than this, it’s just obviously a fair and rational change to make.