For all of the posing and posturing, most of the arguments to extend (or not extend) the size of the electorate to include 16 and 17yos come with a big tinge of self-interest around power. It's been proclaimed that it is "discriminatory" that they don't get a chance to vote, but almost every argument extended to this can be applied to 15, 14 or even some 13 and 12yos. Paying taxes doesn't give visitors or tourists a vote, and plenty who pay little to no taxes get to vote.
No, it's an exercise in emotionally laden performance from those in politics who get an advantage from having more fungible brains to convince to give them power. It's hardly a surprise that there is strong leftwing support for the idea, because it is widely perceived that most younger people (certainly the more politically active ones) are leftwing, because they are lured by the idea of more government, which can make good stuff compulsory, cheaper or free, and bad stuff banned or more expensive. This is, after all, the predominant philosophical bent pushed through state education and much of the media.
Plenty on the right oppose it because they fear it threatens their ability to exercise power, because the ways they want to exercise power are not as marketable to young people when the prevalent culture scorns the values of conservatives and libertarians.
For me, it's rather simple. If there were to be an age when an individual is an adult, in terms of powers to contract, to be treated as an adult in the justice system, and to not have age based restrictions on what you can and can't do with your body, then that should be the age of adulthood. At present it is a mix of 16 and 18, but few on the left think 16yos should face the same judicial treatment as 18yos, and almost none think they should be able to buy alcohol, be prostitutes and even buy tobacco.
There is a curious cultural disjunction between those who want younger teenagers to vote, and demand they be given "a voice" for their often ill-informed, inconsistent views (and they have no monopoly on that), but also think they need "protection" from the consequences of their actions. They aren't old enough to handle being intoxicated, to face adult court and prison if they initiate force against others, and although it is often cited that they can "have sex", it's a serious criminal offence if anyone takes photos of them doing so or even possesses them, even with their consent. So many who want to give them the vote also deem them vulnerable. So which is it?
Consider that almost all of the same Parliamentarians who are supportive of letting 16yos vote, think they need protection from advertising of alcohol on TV (that so few of them watch), but also don't think they should be permitted to buy cigarettes (because they aren't deemed fit to make decisions about their own health). They do think they should be able to apply for a firearms licence and drive though, so work out the philosophical basis for that (clue - there is none).
So let's not pretend this is about young people having a "stake in their future" because the politicians eager for their votes don't think young people can make competent decisions on what they ingest or what photos are taken of them.
If politicians want to argue that 16 should be the age of being an adult, then all well and good, let it be and let them accept the consequences for what this means, and they can vote.
Otherwise it's just a call for "more votes for my side, to help me do what I want to you all"
After all, if you don't trust young people to make decisions about themselves, or take the full legal consequences of their actions, why do you trust them to make incremental decisions on who should have power over others (politicians)?