In these places, this is a great thing to avoid. Old software is well known. You do not want to be the one to be affected by a bug that stops production or changes data.
> mainframes have remained stagnant in features
Having a well known universe without any beta software, and not being disrupted by new stuff that you don't need anyway, is a damn good feature.
I do not beleive that industrial breeding is selecting for anything that makes such prison life tolerable. Birds in production generally aren't reproducing, so nothing in the henhouse is affecting evolution.