The problem is, it's not even just that the band is looking forward, and focusing on just new material, but honestly, it has been a really long time since the band made excess non-album material period. The last "B-Side" that we got, was the acoustic version of Wither. That and Raw Dog, but even that was a half-hearted effort made only because the label asked them to.
My point is, everything they work on these days is meticulously crafted to be on the albums they make, and there isn't any material that gets left on the cutting room floor so to speak, at least that we know of. So it really seems like they just don't bother spending time on "extra stuff", be it old or new, but rather only plan for what's going to be on the album, and how it will flow in the final product. It's a good kind of attention, but for them to just take the time and rework their old material, I don't think they're even in the habit of doing stuff like that anymore.