I think it's the case where they are still pretty new and comparatively unknown.

They have done good work like releasing their paper and dataset for training an assistant RLHF model. https://github.com/anthropics/hh-rlhf

You won't get any dataset like that from OpenAI. It's useful for anyone who wants to experiment with RLHF with LLMs. Which is pretty important as OpenAI is having lots of success with it in InstructGPT and ChatGPT