They should be able to vote for this very reason. However, most don't know what affects different policies will have because most don't respect their elders and talk to old people.
Gotcha. My bad on the first point -- made an unwarranted assumption about your point and apologize for that.

I'm not sure that I'd agree that old people have some monopoly on knowledge or the effects of policies; and I'm not sure that I'd discredit the ability of young people who vote to discern the significance of different policy choices. But I understand your concern.