Because helm charts lack a schema. Programming by yaml configuration means you spend time searching github for an example kind of like what you're trying to do instead of having actual tools which allow auto-completion.

Editing helm charts it the ultimate form of throwing spaghetti at the wall and praying it works, without being able to actually test anything locally.

Example: https://github.com/dhall-lang/dhall-kubernetes

Haven’t used dhall myself but I’d definitely prefer a DSL on top of yaml.