Frankly, this isn't new. When King Crimson reformed in 1983, ALL of their songs were new songs, and they didn't play 21st Schizoid Man or Epitaph. Now, the Crim are still playing songs from the 80's, but most of their recent live repudiator have been recent songs (within the last 15 years.)
When a band's new stuff becomes more popular than the old stuff, they're bound to play more new stuff. And even when it doesn't. When I saw Iron Maiden live, 85% of the show was stuff from 2000-2007; they didn't dig back into their classics, even though their classics are what are most popular.
Sometimes a band *likes* to just do the new stuff. It must be boring, having to play the same songs over and over again. Sometimes they like to shake it up with new stuff.
