The same reason a Turing machine (even a finite one) is a silly programming 'language'. It's an abstract model of computation. It just happens that real-world l

The same reason a Turing machine (even a finite one) is a silly programming 'language'. It's an abstract model of computation. It just happens that real-world languages based on The Lambda Calculus like Lisp are only a stone's throw away syntactically, whereas the gulf between even assembly and a Turing machine program is quite large. I suppose that's because The Lambda Calculus doesn't aim to describe a pseudo-physical machine, and therefore leaves implementation much more open to interpretation.