Turing machines are terribly inefficient, though. They may be easier to reason about than lambda calculus, but not good for practical computing purposes. Their value was in proving that logical and mathematical reasoning could be mechanized with an automatic device, something that had not been clear until then.

Computing science cares a lot about building efficient processes. Thus to create real working programs, a better basis is a combination of lambda calculus for defining mathematical structures and (Von Neumann based) agent-based models for defining stateful processes.

Modern programming languages are evolving to be capable of representing either model, to adapt themselves to the style more suited to the problem at hand.