> Most sites do pay people who write for them. Either they pay the writers, and generate revenue for themselves by advertisements, or if it's an independent website, the website owner gives their time to write the content, in exchange for ad revenue.

Not in my experience. Most offer "exposure" to writers, who go on to die of exposure. Even the sites that pay don't pay much. $20-50 isn't bad for the effort, but you only get it if they accept your pitch.