Infrastructure needs to be consistent, intuitive and reproducible. Imperative languages are too unconstrained. Particularly, they allow you to write code whose output is unpredictable (for example, it'd be easy to write code that creates a resources based on the current time of day...).
With infrastructure, you want predictability and reproducibility. You want to focus more on writing _what_ your infra should look like, less _how_ to get there.
