All those sites have content, which require elaborate, interactive, collaborative editing and reasonably complex, flexible data models. Meaning you’re going to

All those sites have content, which require elaborate, interactive, collaborative editing and reasonably complex, flexible data models. Meaning you’re going to want to re-use much of the work you did for the editing/publishing part and you want those things to be integrated to such a degree that changing and extending things is reasonably ergonomic.