I'm going to go 95% not because of his back problems. I know when they dropped off Warped they used that as the excuse, but he just didnt feel like doing the tour.i
Where the hell do you get that assumption from? Deryck said he loved touring, and I'm sure the whole band was happy to play their music in big stadiums again, even as an opening act.
Also, a band like this can't just stop touring because they don't feel like it, it's basically the only way for them to get money since their album sales are pretty meh.