That would be cool, but human brains are weirdos. If you're already copying text, you could've edited or annotated it, for example. For example, if it's an opinion you don't entirely agree with, you might feel obliged to say so, because you have the ability to do so when it's a text post.

If you want to call that irrational, I'm not arguing against that. I'm just saying it's the reality we live in and I'd like to have tooling to deal with that better, because I would also prefer text to not be screenshotted.