The entire idea of a factory worker is that they can be swapped in place by another and the output is maintained to a great extent. This just simply isn't the case in software or really any creative work. Even if we assume two workers have equal skill sets, something that is already dubious due to the importance of cross-domain knowledge in software, the personality one brings to a team will ultimately alter the entire team, sometimes good, sometimes not so. The social dynamic within groups is a critical element and something that cannot be commoditized away like other professions.
As to the point on commoditization within old tech, I can only answer with a "well duh, It's tech!". The goalposts are always moving within this profession. There used to be a whole heck of a lot of jobs in programming super low-level tasks, those are largely gone and have been replaced with new positions. Last year everyone worked on web apps, this year everyone was on mobile apps, next year it's anybody's guess.