Randomly, I was wondering. Does Jon ever sing falsetto? Pretty much any male singer I know at least sometimes does that. I had to think really hard to remember he sang falsetto in the chorus of Say It Isn't So! This song hasn't been played in 13 years, so is that the only time?
http://youtu.be/OeWnHQ_OCLg?t=1m7s
Even when he went falsetto, he didn't see too confident about it!
If that's indeed the only time, why do you think he never sings in falsetto? It's somewhat acceptable for (some) male singers to lose their voice with age, but their falsetto voice usually still remains in tact.
Lastly, I'm no vocal expert. I struggle to understand the difference between falsetto and head voice. A while ago I tried googling and that didn't help. So, in the mean time, if anyone could explain this once and for all (preferably, with video examples), it would be greatly appreciated!