Most (all?) of the open models worth a damn were trained by corporate giants with practically infinite resources and then released into the wild as marketing stunts. You can't afford to train Stable Diffusion from scratch, and Stability can't really afford to release it for free, it's just an illusion of freedom propped up (for now) by VC money.

These freebies coming from companies like Stability and Mistral are going to dry up real quick once their investors start getting antsy about seeing actual returns on their $billions.