The real world is too complex to analyse. Theory works by analysing a simplified model of the world, with the hope that essential characteristics are maintained

The real world is too complex to analyse. Theory works by analysing a simplified model of the world, with the hope that essential characteristics are maintained and only irrelevant details are ignored. Take the analysis of algorithms. I expect most of the analysis you've seen assumes memory access takes constant time. This hasn't been the case for a long time, due to caching. Now most people don't really care about performance so it's a reasonable simplification. However some people really care about performance and thus need a more complex model. See cache-oblivious algorithms for some work that addresses this. When you get to the level of assembly language optimisations no model is going to help you. You just need to benchmark the code on a real system. Similarly in distributed systems we work from simplified models. This is fine for most of us, but Google has one of the most complex systems in the world. Naturally their requirements are a bit off the beaten track, and perhaps not adequately addressed by theory.