Much of this optimization work requires specific knowledge of the details of the operating environment (e.g. Linux) and silicon microarchitecture (e.g. AVX-512), which can be poorly documented. You have to be comfortable doing experiments and digging into system arcana to surface properties of the system that you can't trivially google. While algorithm selection is important, doing that well is table stakes and part of the role is knowing when and why an "optimal" algorithm is worse than e.g. selectively applied brute-force.

Computational efficiency and throughput is worth a lot of money at scale but most of it is designed and implemented at the scale of a single machine. Every software engineer owns the tools required to become proficient at this. It is genuinely a rare skill even among systems programmers and is a good way to separate yourself from the crowd.