I think the brothers might stray away from releasing instrumental tracks as singles, anymore, for the fact that they dont wanna pigeon hole their fan base.
If you look at the last few singles the brothers have released, they are all pretty unique in the fact they could fit in many different genres, musically. Hence, a broader fan base.
Basically, what I'm trying to say is, the common Chemical Brother fan needs no more convincing. We all know pretty much know the awesomeness of tracks like Burst Generator, Saturate, Das Spiegel and other instrumentals from WATN. Meanwhile, collaborated tracks like Do It Again, Salmon Dance, TPWHYN, and ARR are great selections to reach to the non-typical chemical brothers fan (pretty much for the simple fact that they are collaborated tracks). And once they (non typical fan) get hooked with one of those collaborations/singles, they wanna hear more. So they listen to the rest of the Album, and then realize the brilliance of it, but they still wanna hear more. So then they check out the rest of the Chemical Brothers catalog. And then they find out they are a fucking amazing group. So then they soon become a full fledged Chemical Brother fan, thinking to themselves "And to think, I HATED electronic music."