This study was based in Europe, so may not apply to the U.S.
“Many bodybuilders illegally sell steroids to help fund their own use of performance and image enhancing drugs and maintain their social status in the weightlifting community, a new academic study has found. Researchers at Birmingham City University analysed more than 60 criminal cases and interviewed dozens of people involved in the purchase and sale of performance enhancers in the Netherlands and Belgium, to identify the different types of people drawn to selling the drugs.
The report found that sellers often broke the law to help fund their own use of steroids and that most viewed the substances no differently to high street supplements such as protein powders, energy bars or sports drinks.”
Source: Bodybuilders illegally sell steroids to fund own use and maintain social status, finds report