But maybe I don't WANT to be an expert user! Maybe I just want to USE the damn thing.
It's frustrating when a tool maker thinks that their tool so important that every user must become an expert on every facet of the tool. How about, "The purpose of technical documentation is to teach the user whatever is necessary and sufficient for their particular needs."
I'm a programmer. A few times a year I need to use Photoshop for something Really Simple. I want documentation that can tell me how to draw a rounded rectangle with a shaded gradient inside it (or whatever) as quickly as possible, and tells me as little as possible about anything that doesn't help do that.