Money is another way to measure performance. People that understand these low level principles can write a backend service in C/C++/Java/Erlang/Whatever that can do the work of hundreds of instances of a service written in higher level languages that ignore these concepts. That's not to say that it's never wise to use higher level languages, but these principles can and do save mature established businesses real money.
True, but if my bad python implementation can do the job on one old single core computer with plenty of CPU left over what do I care - in fact because python is generally more productive for small programs it is a lot cheaper. Most programs don't actually handle so much data that they need every bit of performance.
Of course the minority that do need performance are where the real engineers are needed.
