science

That is different from saying there’s no evidence linking it to cancer.

Okay, provide said evidence then.

I'm aware benzene and other byproducts of combustion should increase lung cancer risk, but a wide swathe of studies has failed to ever conclusively establish a connection between cannabis smoke and cancer.

(Also cannabis in California actually is labeled with a cancer risk... not due to smoking it, but due to the presence of the terpene Myrcene, which is why you'll find the warning even on edibles. Still, that's just California being California, as I understand it the warning is there simply because Myrcene has a benzene ring in its chemical structure like many aromatic compounds do.)