Stable diffusion can run anywhere

I didn't set it can't, I said the majority of people who have limited skill set with ML and troubleshooting it end up using the Colab version since it's much more straightforward and easy for average people to get started with.

And that's for all ML stuff, Colab has lead to a huge democratization of ML, with notebooks setups for basically any cool demo you see out there.

Stable Diffusion is severely limited in the memory constrained Google Colab context.