The purpose of the base layer is to keep the ledger intact no matter what. Once you have this and only then you can build payment networks issue tokens whatever on top of it. Lack of confidence? I'm not sure, I would say Satoshi didn't want to make commitments that would risk the general usability of the protocol.

If you look at the OSI model on how the internet works it has also many layers each responsible for one thing and one thing only and it turned out to be pretty good design. 😄