What was the reason of why Billie Holiday (Jazz Singer and Writer) did drugs?

Not long after this event, Holiday was admitted to the hospital for heart and liver problems. She was so addicted to heroin that she was even arrested for possession while in the hospital. On July 17, 1959, Holiday died from alcohol - and drug-related complications. Jul 8, 2014

In 1947 Holiday was arrested for a narcotics violation and spent a year in a rehabilitation centre. No longer able to obtain a cabaret license to work in New York City, Holiday nonetheless packed New York’s Carnegie Hall 10 days after her release. She continued to perform in concert and in clubs outside of New York City, and she made several tours during her later years. Her constant struggle with heroin addiction ravaged her voice, although not her technique.