Also, the nature of the inference may not require high fidelity raw images since they're going to be down-sampled anyway. Unless research suggests that raw images improve inference metrics, nobody's going to invest effort into building a raw image dataset. One notable recent exception to this is the "Learning to see in the dark" paper on low light image enhancement[1] - they found that training on raw images gives much better enhancement than JPEG.
The data availability problem may start getting solved in the near future because mobiles (atleast Android) support storing and processing raw images, and on-device learning and inference capabilities are getting better all the time on mobiles.
[1]: https://www.youtube.com/watch?v=qWKUFK7MWvg&feature=youtu.be