I'll bite.
A 16 year old is (and likely will be for another 5 years) in the mindset of "I'm given money to do things" and not in the mindset of "the money I earn can go on either option A or option B".
Political parties are always offering stuff (and never talking about the consequences of that offer). Labour particularly so.
We have pushed people to staying in full time education or training until 21. Once upon a time 15 year old joined the workforce, as workers or apprentices. They started to understand how the world actually works.
16 year old don't understand that they are living on everybody else's dime (health, education, police, etc)
What 16-21 year old is rationally going to vote against government handing out money (to anyone) when they're currently living with the "be kind" mantra.. It simply doesn't affect them.
The 87 year old is almost certainly living off their own money as well as their state pension. They have 70 years of experience about making choices and unintended consequences.
Sure, they'll probably vote for triple lock and WFP, though many don't, but I'd guess most of them can make more rational and considered decisions than a 16yo