Besides, I would like some benefits reserved for adulthood.

I'd like some benefits reserved for women/whites/under-40-year-olds. What say we disenfranchise men/people-of-color/the-elderly so me and mine can enjoy having special privileges?

Arguments that giving kids the vote would be bad for our democracy is one thing; arguments that adults are entitled to arrogate to themselves privileges Just Because are something else again.