While there definitely are good use cases where rich text clipboard should be supported, for me personally a major use case requires eliminating rich text - where I'm frequently pasting some data from some web system into e.g. a word document and I want to explicitly paste just the text, because it really does not matter what styling the web page used for some ID. Word's "Paste Special"->"Unformatted text" is horribly inconvenient, so currently I just paste it in my text editor and re-copy it, ensuring that only the text remains in the clipboard.