Yes but Kubernetes takes these battle-tested scripts, and allow everyone to use them with a few lines of YAML ;)
I understand the dislike of YAML but a Kubernetes deployment is ~50 lines, if I had to build my own scripts with a similar feature set I don't think I would be able to get it down much more than that.
Also your script often might not be that battle tested, more likely it will have bugs and miss a few important edge cases.