Why do we have to grow up?

I think in some aspects I am not a child anymore, but at the same time I still am. I think that society expects me to act like an adult since I am 15 and in a few years I will have to function in society as an adult, but at the same time society still treats me like a child. I don’t have any rights, my life is controlled by my parents, and I don’t have any control over the world around me. I think it’s cruel that society expects us to act like adults while still treating us like children. I never had any sort of security item, but I have very close friends and family who still do and I think if I had something like that it would be very painful if it were taken away from me. Since I know people who have security blankets and those make them feel very safe and also hold a lot of emotional attachment it would be very hard if that was taken away. I think I realized that I have to let go of being comfortable to grow a few years ago, but I never really accepted it because I always look back at my childhood and miss how happy I used to be and how easy everything was and letting go of that makes me feel like I will never truly be happy with the life I have created for myself.