The answer is: millions of people choose these things, and re-choose them every single day. My niece is a junkie. She has chosen to be a junkie, and she re-chooses to be a junkie every day. This is the nature of evil.
If prayer could help her, she would have been clean long ago.
I understand your take on it. Chemical addiction is physical as well as mental, and tough to break. Millions of addicts stopped making any choices a long time ago...