I heard the tooling for the unique components of the SA were reaching end of life, and given the sales numbers it wasn't financially viable for CZ to get new tooling made.
What you heard may be right, but that seems like an "idea" rather than a good explanation. I wonder what unique components require specialized tooling?
The slides for both the .40 and 9mm versions are slightly different than the DA/SA versions, but the 9mm or .40 versions could be used if a SA model was still wanted, and it would be only slightly different, and the slides from the SP-01 or Shadow are also compatible. The frame itself is cast.
If you want an extended beavertail -- one of the things I liked about my 9m SA -- that's available in other models such as the SP-01 and Shadow, and those models have a rail; I know that's a turnoff for some shooters, but it hasn't hurt sales of SP-01s and Shadow models. There's nothing really different about the internal parts of the SA except for the trigger lever (no big deal) and there's no connector -- but except for that, the parts are the same for all 75B-based guns. (Disconnector-equipped models have a slightly different hammer with one less hammer hook.)
CZ also discontinued the 85 Combat, and probably for what is likely to be the same reason -- not enough demand to bother...