Why?
Why not? This is how all other simulators - to include all certified training devices and simulators - work.
Now, why do you think they work that way?
Because those of us that use them to train pilots in the real world need them to work that way.
So why wouldn’t you want MSFS to be able to do this as well?
You seem to be using “volumetric” to mean that the weather cannot or should not be constant throughout the entire world. This isn’t really the literal definition of the word, but if I’m understanding correctly I can see how you’re using it. But we keep explaining to you that in many training scenarios, we NEED the weather to be constant throughout the world.
Now, how would YOU accomplish this? I want to tell the sim I need to remain solid IMC with not a single glimpse of ground, blue sky, cloud structure or lighting change, until seeing the first approach light at the exact moment I specify. I want to be able to fly 100 approaches in a row to one airport without any variability at all, then divert to another airport 50nm away and see the exact same conditions.
How would you have the sim accomplish this? And given that it’s a requirement of real training vs entertainment flight simming, why wouldn’t you want the sim to be able to accomplish this?
Again, we aren’t talking about changing how live weather works. We’re talking about allowing the user to actually control the weather when necessary - something we’ve always been able to do in previous sims.