They may not have a choice. Fighting these legal battles is very expensive and exhausting. And books are a low margin business. Anthropic has access to funding. Authors? Not so much. Losing your book to AI for a one time $3000 settlement feels like a bad deal to me.
It isn't about sales in the short term. Same with code. Your project might even be OSS (so not expecting profit). Its about a system that exploits that for one party's profit, while putting the other out of business. They reduced the writer's ability to ever be employed again, or to make royalties at the same level as before (not necessarily reduced the sales of existing titles, though that may occur as well).
Same with code, AI hoovering all the code doesn't mean people won't use libCurl, but it does mean jobs are disappearing and people may not be around to write the next libCurl.