Comment by rahimnathwani

  The problem is that even for things like consoles, it's usually more "cost efficient" to write normal fast-to-write code that isn't maximally effective, let the compiler do its magic, and call it good enough.

This wasn't always the case. I have a friend who used work on games for the original Playstation. I remember him telling me that part of his job (or maybe his whole job) was optimizing the machine code output by the C compiler.