I think that some people just automatically assume that people who have a high level of athleticism/speed/power/physique are on some type of performance enhancment drug. And many times they are not. I'm not saying that people don't use PED's. But their are so many people out there that are just God blessed with raw talent and are strong as oxes.
The combination of strenious scientific spefic training regiments, healthy diet/nutrition, genetics and overal raw athleticism is the common denominator for athletes such as Westbrook, LeBron, Adrian Peterson, Barry Sanders, Brandon Marshall, Usain Bolt etc. I think that some people see these athletes perform at elite levels and exibit athletic feats at levels that the average person can not comprehend, the automatic thing they assume that no human being can actually do that without juicin etc.
And in many cases, that's unfair
If you clap your red shoes, you might make it back to Kansas Dorothy.