But that's really no different from discrete manufacturing, where you have to track precious metals, hazardous materials, import/export regulations, etc. I wonder why the major players don't just make the minor adaptations so they can serve this market, too.

Likely federal law. Its not settled legally if providing services to recreational dispensaries can implicate your company in felony drug distribution. Its unlikely, but a risk. It may even cause issues with the bushiness main product. Things like insurance liability shifts and the like.

No "big name" company has wanted to test the waters.