Companies are just resistant to change, period. It's a feature of human nature and is exacerbated in many companies cultures. Legacy stuff will always have an intrinsic advantage simply because it's low/no risk. New stuff always comes with some risk and most cultures within organizations are risk averse. The larger and older the organization the more true this generally is.

I wrote an article a while ago about this phenomenon in a DevOps context and how to overcome it: https://calebfornari.com/2019/12/28/subversive-devops/