Incidentally, it's a mystery to me why so many of the Gutenberg/Internet Archive books have such ludicrously bad plain-text renderings, utterly unusable/unreadable, with often barely one word correct per page - since neural nets have been getting very high scores on MNIST handwriting recognition (for example) for a long time now, maybe since the 90s? It's a shame.
https://cogdogblog.com/2013/12/recaptcha-all-the-books/
The current one helps in identifying and navigating streets, useful for maps and autonomous driving.
https://techcrunch.com/2012/03/29/google-now-using-recaptcha...
You'll notice that recaptcha always has a direct effect on current projects of Google/Alphabet: Google Books, Google Maps, Waymo.