Cycling is the flavor of the month right now. Bodybuilding, Weightlifting, and certain areas of Track and Field are long known drug sports with no really known name athletes, so people will just shrug when they hear about them. Cycling had a huge star attached to it, and lots of fans because of Armstrong, and he's a American, so it gives the politicians here something to crow about.
Baseball got it a few years ago, the NFL is great at handling the press, The NBA seldom gets mentioned as far as steroid use, Hockey doesn't have a big following here so they're safe, etc.......
Track did catch some heat a few years back from the Balco investigations, so that buys them time, but I wouldn't be surprised it Bolt, etc..... start getting looked into more in the next couple of years, I noticed that he was being brought up a lot in a questioning way after the 9.79 documentary, and for him maybe having a known drug cheat on his coaching team.