Earlier quoted context omitted.
So should Apple have kept compatibility with 32 bit apps? PPC apps? 68K apps? Apple does release security fixes and released one for the 2012 circa iPhone 5S last September. But once it dropped support for all 32 bit apps, it didn’t have to carry it forward to new Macs and was able to remove support from the processor itself.
Why not? Given Apple's growth, they can hire a person for every release of their OS and keep them working on backports of security issues without problems.
Why stop at software compatibility, why shouldn’t modern MacBooks come with SCSI and ADB ports? Why shouldn’t Apple desktop computers still support Nubus?