"an unlimited and open local tool" -> Not everyone has GPU or powerful machines.
Also, you can run it locally on a non-powerful machine. It just takes longer, but you can also just queue up as many prompts as you want and let your machine crank them out at its own pace. I use a first-gen macbook air m1 and it usually takes ~90s to generate an image with my usual settings.
Plus integrations into other applications like Photoshop and Canva. Open source has such a huge multiplier effect for innovation.
For anyone else stability offer a paid web version.