On the other hand:
How many additional EF-S lenses Canon ever created for APS-C cameras?
Just 3 = 10-22, 17-55 and 60-macro?
The rest of EF-S family are 'kit lenses' for this or that camera model (18-55, 55-250, 17-85, 15-85, 18-135 and 18-200). These lenses were needed to make specific camera models attractive to some target users at some point in time.
Those who purchased 7D are supposed to use its 'kit lens' = EF-S 15-85. If they use EF 300 lens with 7D -- they are probably regarded by Canon as 'cheaters' who managed to get away from purchase of 5D.
So it looks like: Canon never treated APS-C cameras too seriously. These cameras were needed and intended to bring new users into EOS system. APS-C camera users were supposed to purchase EF lenses (with existing EF-S lens lineup being so limited) and to make a switch to FF cameras 'some time later' (= now!).
PS: This could be the reason why Canon tries to cripple or limit EOS M and its EF-M lenses and will be the last camera maker to release mirrorless FF. The situation with EOS M is not like with usual DSLR APS-C users, the chances that new users of small and tiny EOS M will ever purchase EF-EOS M adapter and EF-S or EF lenses (including big whites) are close to zero -- these are just too large for this camera...
Interesting post, I think you may be right.
5D3, 5D2, Sony α6000, G16 | EF: SY14/2.8, V20/3.5, 28/2.8 IS, Ʃ35/1.4, 50/1.8, 50/1.8 STM, Ʃ50/1.4 EX, 100/2.8L IS Macro, 16-35/4L IS, 24-105/4L IS, 70-200/2.8L IS II, 1.4x II, 2.0x III, T28-300 VC PZD, 70-300L IS, Ʃ150-600 OS HSM S | E: SY12/2, 35/1.8 OSS, 16-70 ZA OSS, 55-210 OSS, SY300/6.3 ED UMC