Steven has released his albums in both CD + surround disc and standalone CD and surround disc configurations - you have to assume that if he's doing it as two seperate releases it's because sales data for previous releases probably shows they'll make more money this way.
The days of bands selling hundreds of thousands or millions of copies of an album are long gone at this point - I recall Steven saying in an interview that Grace For Drowning had sold about 8,000 copies on BluRay at the time the interview was done, and that that was a really good sales figure for a BluRay audio disc. Labels need to be very careful about what formats and configurations they offer because having a few thousand unsold units (especially of BluRays, which I believe cost a few thousand dollars per 1000 units just for the disc pressing) can be the difference between something being a financial success and failure.
We have to accept that as people who buy surround music we're a niche market and will always be in the minority, and that the logistics of the release format meant for mass consumption (ie the CD, or digital download) are always going to trump what we'd like. Look at it from the perspective of someone who only wants the CD - people like that probably outnumber us 25 or 50 to 1 (or more). All they want is to pay $10 for a CD, not to be forced to pay $25 or $30 for a CD + BluRay set. They bristle at that the same way we bristle at having to buy expensive box sets with vinyl in them (or things like the Ten Years After quad DVD + vinyl set) because the BluRay disc has as much use to them as vinyl does to us. Record companies also have to be aware that there's basically a 'piracy threshold' with pricing: if you price your product too high there's a point beyond which people will say 'screw it' and just burn a copy off a friend or download it off the internet, and neither is hard to do even for the most technologically backwards.
If you really need a CD of this new album, simply rip the BluRay, extract the stereo audio track and downsample it to 44.1/16 bit stereo .wavs and then burn it on to a CD-R. In the US and Canada (I believe UK copyright law has literally just changed to make this illegal once again) you're allowed to make backup copies of albums you own for your own personal use. There are plenty of tutorials on the internet that will tell you how to do so, and you're probably saving yourself a few bucks by only buying a standalone BluRay instead of a two disc combo set.