I think it's because there are two cases that require flawless performance: when you are pushing the limits of the hardware, and when you are adding a layer tha

I think it's because there are two cases that require flawless performance: when you are pushing the limits of the hardware, and when you are adding a layer that people will build lots of software upon. Games are a perfect example of the first case. Have you seen how much optimization goes into the rendering of a modern 3D game? They are not wasting hours to shave a single byte like the olden times, but the whole thing is piled with low level optimizations. And languages are an example of the second case, where you are adding a layer. This is crucial because layer performance is compounded. If the OS is using 75% more operations than it should be, and the language is doing the same, the final application slowness goes up by 3x. Sure, your smartphone app should conserve battery, and it would be nice if it finished its operations a tad faster. But that's a case where you don't need to scrub assembly code.