It seems the problem here is that most don't want pancake lenses. What I see a demand for is Ef-s primes with fast apertures and not that much emphasis on size.
Wow. What you can see is immense. I think the opposite. Suprised? There is a lot of demand on the 40mm 2.8 STM, I own one by myself and I'm always surprised what this small thingy can do. At the moment this lens is nearly always on my cam.
So, if someone travels around with a smaller APS-C the 40STM or 24STM could cover most of the needs...
Where is the demand on fast primes on APS-C? There already are fast primes in this focallength-range like the 35mm 1.4L or 24 1.4L. I just don't think that you're willing to pay the prices...
One small tip at the end, maybe you don't know. There are a lot of primes in your range... for example the EF 20mm f2.8 or the really fast EF 28mm 1.8
. They're comparable cheap and still to get.
I say again that I am not against Canon release lenses that do not meet my desire. The sad part is that the launch of an EF-S 24mm F2.8 means that Canon will never launch an EF-S 22mm F2.
They have a 24mm 1.4! What about this one?