[posterboy]

> LC was a very (the most?) efficient route to factorial calculation

It is, because it is a standard model for computation. To put it in layman terms, every programming language is lambda calculus in disguise. You have absolutely no idea of computability theory. That is the theory in which the P=NP conjecture is formulated, which has massive implications e.g. on cryptography.

You seem frustrated for not understanding at all what's going on here and you try to provoke answers. I know what I'm talking about, because I don't grok LC either and I get furious quickly when I'm hungry, tired or overworked. You are paranoid.