I was with you up until the last paragraph. Taken literally you seem to suggest there is no such thing as a CPU-bound workload. That's obviously not the case (cryptography is just one such example), but I would agree that many people think they are CPU-bound when they are really constrained by something else.

Secondly, Python and the patterns its expressiveness encourages are terrible for cache performance. In a simple C program it's easy to do something non-trivial in the space provided by L1 cache — in Python it's quite difficult even to reason about what's going to be in L1 if you're using any of the fancy features.