It's wild to me that a paragraph or 7 of plain English that amounts to "be good at things" is enough to make a material difference in the LLM's performance.
There will always be bosses who/which think telling workers to work well works well.
They have no values of their own, so you have to direct their attention that way.
As the base is an auto-regressive model that is capable of generating more or less any kind of text, it kind of makes sense though. It always has the capabilities, but you might want it to emulate a stupid analysis as well. So you're leading in with a text that describes what the rest of the text will be in a pretty real sense.