Automatic1111 and ComfyUI implemented the SAI backend/format in the early days because thats all there was, and now they are stuck with it. The intertia is tremendous.
It seems like an odd move to me as what makes Auto1111 so appealing are the extensions and I’m assuming that breaks an awful lot of them, but what do I know?
On top of that HF is just hard to use for your average user. Civit.ai is just "click to download" while HF is "look here's a broken model card... you can figure it out from here".
Despite the cute logo, I think most people find that HF comes across as fairly anti-user. Despite having years doing ML related work, I still find HF a bit byzantine to navigate.
Technology-wise, path dependency from stuff that was built out before HF diffusers were available, and on which more continues to be built in the ecosystem.
If you are doing a greenfield project that is mostly standalone, its not an issue, but for existing popular projects and the communities of satellite projects around them, the switching cost is high.
In terms of content hosting, well, a fair amount is hosted on HF, but there is a difference of content focus between CivitAI and HF, and a lot of what CivitAI hosts HF probably wouldn’t want to. Also, CivitAI has a UI focused on the narrow space of imagegen, whereas HF is more general.
