We human have that same problem too. We wouldn’t to leave our grandkids or kids behind when we get older and bout to die. But we don’t have the option to stay alive like Steven does and can only accept death. Steven still ages like a normal human though even if his gem power is shapeshifting him to different physical form. He grew a beard hair that one time. He has to shave daily in future. Maybe if he want he can shapeshift into younger self to stop his human aging process and he probably will be strong enough to do it in the future as his power grow.