Why are parents always blamed for how their adult children turn out?

I am overwhelmed. I am astounded how often I hear a parent being blamed, faulted, and criticized for how their adult children turn out. Earlier, I asked for help. I asked a simple question and in return, I received unsolicited reprimand. My daughter was a teen mother. She remained married to the child's father for 3 years at which time, she asked if she and her son could come and live with me. Essentially, I raised my grandson while his mother enjoyed complete freedom and the opportunity to receive her college degree. When she graduated and no longer needed a "substitute mother" for her son, my money, or my home, she left and severed the relationship between me and my cherished grandson. He has lost the memories because he has been lied to and denied the truth. I immediately received a reply suggesting that I took control, questioned her parenting, etc. So far from the truth. She did NOT parent. Why must I be blamed instead of looking to my daughter for accountability?