The bare minimum cost of software churn is the effort of one human being, which is far less than hardware churn (multiple layers of costly design and manufacturing). As a result, we see hardware change gradually over the years, while software projects can arbitrarily deprecate, change, or remove anything at a whim. The dizzying number of JS frameworks, the replacement of X with Wayland or init with systemd, removal of python stdlib modules, etc. etc. have nothing to do with new additions to the x86 instruction set.