Because they want to influence the mainstream outside of their frontiers.

Using local models, usually means generating content on a more private, local device with the weights of the model stored on that device - a local LLM model could have helped write these posts. It only gets easier to self-host increasingly capable models for generation of text, images, video etc. E.g: Prism ML Bonsai have an older 27B text generating LLM model squashed down to a few GB at what they describe as 95% quality, which can run on a phone.