This is the scenario: a guy, say age 21, becomes serious about gaining muscle. He’s 5′ 10″, 7″ wrists, 9″ ankles, average genetics for muscle size-and-proportioned. He’s played sports, but never done more than an occasional resistance workout. Now, he begins a good training-eating-and-resting program. With his genetics, he has the potential for naturally gaining 45 pounds of lean mass if he stays consistent with progressive training/proper eating for a continuous 3 to 4 years.
But, about three months after beginning his training, he starts taking steroids. He does three steroid cycles in the following 18 months, and includes proper post-cycle therapy. That entire time, he’s continuing to consistently train and eat properly. Before the end of two years, he’s gained 45 pounds of lean mass (which with steroids, by the way, is not necessarily typical but neither improbable). At that point, he permanently quits using steroids, but he does continue properly training and eating for another two years. At the end of four years, he carries the same 45 pounds of lean mass.
Heavy consumption of the essential amino acid lysine (as indicated in the treatment of cold sores) has allegedly shown false positives in some and was cited by American shotputter C. J. Hunter as the reason for his positive test, though in 2004 he admitted to a federal grand jury that he had injected nandrolone.  A possible cause of incorrect urine test results is the presence of metabolites from other AAS, though modern urinalysis can usually determine the exact AAS used by analyzing the ratio of the two remaining nandrolone metabolites. As a result of the numerous overturned verdicts, the testing procedure was reviewed by UK Sport . On October 5, 2007, three-time Olympic gold medalist for track and field Marion Jones admitted to use of the drug, and was sentenced to six months in jail for lying to a federal grand jury in 2000. 
Finally, the life of a steroid-user is not as glamorous as it seems. Steroids are expensive and illegal. They can do jail time if caught, and there are a lot of ancillary drugs and supplements that must also be taken to minimize the damage to their organs or to keep certain hormones in normal ranges (ex: Nolvadex). Their bloodwork (hematocrit, cholesterol profile, etc.) and blood pressure is often atrocious. They battle with sleep apnea and fluctuating moods and sex-drives, and many have trouble performing simple daily task such as wiping their butts or washing their backs. Last, their caloric intake is much higher (and expensive), and it becomes a chore to meet calorie and protein requirements day in and day out. The grass is not always greener on the other side.