Why do academic celebrities self-plagiarise?

I’m not searching for self-plagiarism but I increasingly spot it when reading. It’s a vague itch of “I’ve read this before” and the search facilities of digital books (Google Books, Kindle etc) makes it easier than ever to confirm. I noticed recently that a paragraph of Zizek’s recent Russia Today pieces on Covid-19 (which one expects will be reproduced in his forthcoming book on the subject) was directly lifted from his recent book on digital capitalism. I noticed the same thing when reading Rosi Braidotti’s The Posthuman (2013) which contains a passage I had read a few days earlier in her Posthuman Knowledge (2019):

Why do they do this? I understand reproducing ideas as a condition of accelerated knowledge production: demand for the ideas of academic celebrities outstrips their capacity for supply hence the necessity of reiteration. But why directly copy and paste when it would take a few minutes to simply paraphrase? I can’t help but feel it shows a contempt for the readers who are buying these books latent and unacknowledged within what I suspect the celebrities experience as their own rushing sense of self-importance.