Point of sale tracks the SIM, but unfortunately a SIM is probably still not generateable onto blank cards?
I've heard of sim cloning, never tried it. https://www.techwalla.com/articles/how-to-clone-a-sim-card
If you mean generating a new sim from nothing, sounds cool, not something I'm experienced with personally. I think of the data on the sim as the "login" information for the cell provider, so that might mean either being a cell provider or stealing service.
I see there is value to anonymity. Hard to think about.
I'm thinking if you figured out the insides of a sim card you could probably social engineer some support reps to get the needed data for your account to generate your own sim. Not sure how you'd pay for the account. I bet in some area they have community sim cards.