Because you'd be a stupid, naive motherfucker to believe that there isn't/wasn't a widespread PED use at the highest, elite level of athletics.
Or, number two, you're an insecure fucking pussy to compare yourself to others that are stronger or more athletic than you. None of these concerns should affect your goals in any shape or form if you're a fucking noob to the Iron Game, or unless some asshole charlatan who claims to be natty but really isn't is trying to sell you some bullshit.
*ahem* Mike Chang, Kali Muscle, CT Fletcher, feel free to go fuck yourselves.
Why are people so concerned about what grown-ass men decide to put in their fucking bodies? Who gives a shit? Unless you're a 100% legit drug-tested athlete who's competing against other dudes that may/may not be natty, I wouldn't be fucking concerned about who's enhanced or not. It's not my fucking business, nor does it affect my goals and progress whatsoever.
Now. Go rent Bigger, Stronger, Faster* by Christopher Bell and enlighten yourself. Or don't. I don't give a fuck.