Because Gatlin's negative image around athletic world is off the charts. So anyhow he's condemned by the majority of the fanbase,
Contrary to that, IAAF quickly said that blood values of Bolt, Jessica Ennis and Mo Farah (probably the 3 most "charismatic" athletes in the world, or the 3 most marketable and known athletes) aren't abnormal. It's all about money, people attending track & field events, marketing, etc.
In the same lines, nobody mentioned Yelena Isinbayeva, although she was on every Russian team during the last 10 years. But now she's on a break (oh, casuality!)