What is doc as code? Doc as code is basically two things. One, it's creating documentation with the same tools as you would use to create code. Two, it's using similar methods of creating, versioning, and publishing documentation as you would with code.
What do I think about this? Short answer is context. If you're creating or editing material in a software environment that uses Agile methodology, then you should doc as code. Otherwise, I wouldn't worry about it. If you're in this context, I'll give you a few, brief reasons why you should doc as code.
Save Costs
The first and foremost why you should doc as code is to save costs. Tools, licensing, even training on how to use tools all cost money. It also costs time to maintain and invest on different tool sets. If you're using the same tool to create code and documentation, you can save on both. No further explanation needed.
Easier to Build Bridges
If you're using the same tool as your Subject Matter Expert (SME), it's easier to build bridges to create documentation. If you're using the same tool(s), it's easier to collaborate together on documentation. This doesn't mean you have to learn to code. (But it might help to know a little bit.) In some ways, using the same tools and releasing documentation the same way as code is like you're speaking the same language as your SME.
More Unified Experience
If you doc as code, then the release of software and documentation is much easier. The obstacle of getting your documentation in a certain format, so it goes with the software release is no longer an issue. You just have to make sure you and your SMEs are working in sync to make sure the documentation reflect what's in the code and vice versa. And that can be challenge in itself, so why would have other unnecessary issues to prevent this from happening.
To find out more about doc as code, check out these resources:
https://www.writethedocs.org/guide/docs-as-code/
https://www.gitbook.com/blog/what-is-docs-as-code
https://github.com/readme/guides/code-as-documentation