The transistor can only get so small before it stops working.
There are many issues with required extreme ultraviolet light sources (lasers) and allowed amount of impurities in silicon waffer. And R&D cost for each iteration of lithography is getting higher while bringing less benefits.
Yes, the existence of an upper bound on transistor count follows easily from the atomic nature of matter. The Wikipedia article on Moore's law lists multiple disparate "enabling factors" which do not seem to have much to do with one another. The conjunction of which comprise an explanation of sorts, but I'm wondering whether there's a simple observation or fact that ties them all together, apart from my Sociological theory.
The transistor can only get so small before it stops working. There are many issues with required extreme ultraviolet light sources (lasers) and allowed amount of impurities in silicon waffer. And R&D cost for each iteration of lithography is getting higher while bringing less benefits.