Aloha !

The reasons songs don't get played live is because Jon tries out the ones he's most confident of first (either his own vocal capabilities or what he reckons works best with a crowd), and then when he realizes those are the ones that work, he's not willing to try out anything else unless there's serious demand from the fanbase for a certain song.

Another factor that comes to mind is with todays way of recording, often songs haven't been fully played live by the band ever as they have never demoed them as a band before recording. Drumcomputers, many different guitars layered one over the other and then none of it can be replicated live, especially not on top of Jon's doctored vocals nowadays.

Salaam Aleikum,
Sebastiaan