This is an R&D cost thing and the right analogy is to the telephone operator. It obviously cost a lot more to build even the first electromechanical last mile exchanges (with Strowager / SXS switches) than to hire some young women to work as operators, let alone to design something like System X (a computerised telephone exchange used in most of the UK from the 1980s) but you don't have to keep paying for the R&D on an ongoing basis. The girls married, or got less boring jobs, or just left work, each time you must recruit and train replacements - but you design System X once and use it for forty years no problem.

There are still System X exchanges in the UK to this day, it works fine, so why not. Eventually as copper last miles are discontinued these exchanges will be virtualised, and in some sense System X is then banished to museums like the Strowager electro-mechanical systems I saw as a child.