Everyone is affected by government policy, but the disparity between representation and responsibility is greatest between those aged 16, who cannot vote, and those aged 18 who can.
Everything from education policy through to health and social policy can have an immediate effect on 16 year olds have no say in who represents them at a national and local level. At 16 a person can join the Army, but not vote. A 16 year old can work, but not vote. A 16 year old is old enough to be tried in a court and punished for breaking the law, but cannot vote.
Reducing the voting age will also increase the political and democratic engagement of young people. Getting younger people involved in the national debate early, ensuring that they have a stake and a say, should improve the political discourse more broadly.