I saw an interview asking him why the album was so 'depressing' and whether it was because of bad personal experience. Jon replied that they felt great when they wrote the album and that the sound they ended up with was what felt natural at the time.

Maybe we don't see so many TD songs anymore because they're off a more serious album which Jon might see as being too serious or slow for playing on really exciting live shows. Another possibility is that becuase this album was written when his vocals were arguably at their best, they have become harder for him to sing at such high quality. Whatever the case, I'd like to see some more TD tracks live on tours.