Why is Leftwich not a pure - ping star in NFL, yet ?

I like the pure ping style, I enjoyed watching Dan Fouts, Dan Marino, Kurt Warner, etc.... Leftwich, I thought, would be the next guy to do this, judging by college, style, and arm strength. Why has this not hapened yet ? Also, whom will be the next pure ping QB to rival Manning, whether from college or the pros. Rivers, Brohms, Jamarcus Russell, who can challenge Marinos', Favres', Mannings', Warners' records ?