I have actually thought about this a lot. I think the answer to your actual question (why not?) is obvious: people with the capital+skills to start this up do not have a solid profit motive. People who would benefit from it don't have capital+skills.

However I think setting up something like a worker-owned cooperative to replace various gig economy companies would be a really cool project. Honestly if such a service existed, and my friends continued to use the (cheaper) VC-subsidised option, I'd ostracize them for it.