The Supreme Court at least since the 1920s has asserted a parentalright to control the upbringing of their children. (Scalia, naturally, dissents.) And in 1979 the court held that right to control includes decisions over medical care.
Progressives who support the right of fifteen year old girls to make decisions about abortion without parental notification do not trust these same girls later in life to make their own investment choices with their Social Security funds.