It was easy to throw hardware at a sequential problem, a decade ago. CPUs were still improving their single-core performance year after year, and memory access and all kinds of IO devices kept getting faster and better. I'm guessing that time was where this idea originates from.

Today, things are different. Single-threaded performance isn't going to be improving much in foreseeable future; the effort shifted to improving parallel performance and, more recently, power consumption. So if you write slow code - perhaps by choosing a slow software stack - your code will remain slow.