Turing completeness may not be that important in everyday programming, but it's at the heart of CS just like (to pick a lame example) conservation of energy is

Turing completeness may not be that important in everyday programming, but it's at the heart of CS just like (to pick a lame example) conservation of energy is at the heart of physics. What still baffles me about Turing completeness is how ubiquitous it is. Everything from Conway's Game of Life to C++ template specialization to Ruby is Turing complete. Only the latter has been explicitly designed for general computation; for the others, it just "emerged". It's almost as if Turing completeness is an aspect of nature, and it takes work and artificial restraint to design an interesting, powerful mechanism that is not Turing complete. I find that fascinating.