Why has the writer written this text?

(If you aren't talking about the website, then this answer isn't applicable to this situation.) It depends on what you are talking about, but if you are talking about this website there is no need to ask that. You are voluntarily coming onto this website and reading questions/asking questions. This is a public site which everyone can use and anyone can answer questions. You may think that their answers are crap but not everyone writes crap. I know that this probably falls under your definition of crap, but you asked the question.