This has been the thesis behind our product since the beginning (~3 years), before a lot of the current hype took hold. I'm excited to see it gain more recognition.
Chat is single threaded and ephemeral. Documents are versioned, multi-threaded, and a source of truth. Although chat is not appropriate as the source of truth, it's very effective for single-threaded discussions about documents. This is how people use requirements documents today. Each comment on a doc is a localized chat. It's an excellent interface when targeted.