Orchestration tools (which also include chef/puppet/etc.) inherently need to be able to notice when something is just a little out of whack, and respond by just calculating the smallest action that will restore things to the way they “should” be.

Unless your scripting language is both deterministic, essentially syntactic sugar for a dependency digraph that the orchestration system knows how to calculate reduced patches of, it’ll break the “convergence” abstraction of the orchestration system: in est, it won’t know for sure what state the system is in after the script runs, so it won’t know what needs to be done to put the system back into any other state later on.

Not that such scripting languages don’t exist. Apache BEAM, for example, is a set of SDKs for various languages that let you write code that compiles to dependency+data-flow digraphs. But it’s probably not the type of scripting you’re thinking of.

I should also mention, though, that systems like k8s do allow arbitrary programming (not necessarily “scripting”) through Operators (https://coreos.com/blog/introducing-operators.html). Rather than scripting the orchestration system itself, you write a new type of component for it to orchestrate, where that component is both created/managed by the orchestration system, and, through delegation, is responsible for implementing the method by which the orchestration creates/manages other specified types of resources.