Why should we be thankful to our parents?

No-one asks to be born. No-one makes their parents keep them. Your parents can get an abortion, give you away, they don't have to keep you. I know we should be grateful if our parents are good to us, or give us the best life we can, but why should we appreciate them feeding us when we were babies and keeping us when we never asked? I hate how I'm living in a world full of hate, misery and greed. I get strongly affected by the injustices done in politics, the suicides by children. Why should I appreciate my parents bringing me into this?