According to a study by the US Election Project, the age group of 18-29 had the lowest voter turnout, compared to the highest group of 60+. Similarly in the UK, only one out of every three young adults able to vote are even registered to vote. If young people can't even be bothered to register to vote, why should they have the right to cast their ballot? The voting age should be raised because the higher age categories are much more likely to actually register and vote. Ballots don't need to be wasted.
Low turnout isn't a reason to change the age requirement. It says something about the society's attitude to young voters. Perhaps education on voting and electoral issues should be implemented before elections occur, rather than completely isolating a group from their individual rights.
[P1] The young voting demographic has a low turnout. [P2] Accurate voting requires a high turnout.
Rejecting the premises
[Rejecting P1] The proportion of young people that vote is growing.