Because there is no superdelegate voting until June 3rd. Doesn't matter how many superdelegates announce their pledges in the coming days. If the jug-eared jackass says something really bad, or if his terrorist and radical connections further alienate patriotic Americans from him, there is always the chance the party will decide to support a moderate, non-elitist friend of the common man who respects American values.
Or even Hillary, for that matter.
As Bono said, "Charlie Manson stole this song, and now we're stealing it back."