I see no reason to get into specifics as to why this is so -- it's not an interesting line of inquiry, and it distracts from the man's remarkable capacity to craft a song that climbs into the deepest caverns of a person's lonely heart. He knew his voice, he knew exactly what he wanted to hear from it -- that's what he brought to the stage and the platter, and that's why people loved him.
Three things, however:
1) Listen to the kids. My takeaway quote from Bill (not the Rolling Stone) Wyman's excellent memorial of Petty:
While Petty’s image was laid-back, almost hippielike, you don’t get to be a star and stay one without some grit. His kids, he told Zollo, know the truth: “They said, ‘The world pictures you as this laid-back laconic person, but you’re really the most intense, neurotic person we’ve ever met!’”2) Further to 'Point #1 (above): watch Peter Bogdanovitch's Tom Petty doc Runnin' Down A Dream. Think four hours is too much time to devote to the subject matter? Think again. I've watched this doc twice and am queuing it up for a third viewing. And I'm not a fan.
3) This picture, circa Damn The Torpedoes:
Quite the achievement. Godspeed and God rest, sir.