Something like this would only make sense if it's f/2 or faster. 17-55 f/2.8 IS covers the range and has IS. Yes, it's more expensive, but it's focal length range is useful.
I disagree for form factor reasons. If it's a pancake lens, there's your value proposition. It might not be for you, but many folks would love to turn their APS-C rigs into inconspicuous + easier-to-bring-with-them-everywhere 35mm FF equivalent walkaround setups.
So I think that a fairly quick (say F/2) wider prime in a pancake format would be very well received I think.
I don't necessarily disagree with you, but what if it was a f/2.8 lens without IS like the EF 40? I see little value in that. A person bringing both the 24 and 40 and possibly something else might be better served by the 17-55. Either that or pick up the M with the 22 f/2, which is still less inconspicuous than an APS-C body.
This gets to the specificity of shooters' needs:
If you want a tiny camera/lens size + an AF prime in the 24-50mm FF-equivalent focal length + APS-C sensor --> EOS-M + 22mm pancake (plus a lot of Fuji options)
But if you want all that with a proper optical viewfinder, you are out of luck. Some would say that's too picky a combination. Give up one of your requirements: you could opt for an MF lens on an adapter, a large 20mm or 24mm prime with an EF mount, or use the 40mm pancake with an effective FL of 64mm.
Others might get a P&S for that need.
And others would celebrate more pancakes from Canon. I imagine that I'm not the only one.