Why do my parents still treat me like a child....at 19 years old?

My parents are so overbearing and overportective that its making me suicidal. They almost never let me go out with friends. They wont cosign a loan to ge me a car loan so i have to drive my dads honda. Its a good car but i hate pratically begging to use his car every time i want to go somewhere. I have a curfew. You heard that right. A curfew at 19 years old. Anytime I leave he house I have to tell them where I'll be and what time i'll be back. If I'm so much as 5 minutes late I'll get scolded like i'm freaking 14 and for not calling them to tell them i would be late. They won't let me go to the beach with friends or even smoke. They caught me smoking once and threw away my cigarettes and gave me this lecture about how smoking causes cancer. As if i didnt know that. I have low self esteem, very few friends and basically sit around at home all the time. If there was a painless way to kill myself I would have probably done it by now. How can I get respect from my parents?