I think they have so much success with Adobe Fresco on the iPad they don't see a reason to bring it to the mac computer. I think the idea behind fresco was forward to be an app for tablets. But because Windows has so many different types of computers they went ahead and created it for computers as well so that I would work on things like the surface pro and stuff. But on the Mac side it's been very successful on the iPad Pro so I'm thinking they don't have a reason to put it on the actual computer. That's just my theory.
But if you want it on the Mac computer you can always go to the Adobe wish list and requested. You go to the website and go to the bottom of the page and click on select product click on fresco and request if you put on Mac computer. https://www.adobe.com/products/wishform.html