I’d say most of Genius’ visitors comes from the “song x lyrics” so hiding those with robots would ultimately make them lose almost all of their traffic.
Not due to robots.txt but you can see what happens to genius formerly rapgenius when they get removed from the index:
To be fair to TC, if you disable JavaScript you get a pretty good experience - just the full article, legible. Not like those sites that require JS to load the text and/or images.
But you need JavaScript to get past the "we value your privacy, so give us permission to sell it" banner.
robots.txt is designed to keep garbage off search results. It has absolutely no power to prevent a bot to do anything. Also if the site added robots.txt they might as well shut down because their entire userbase comes from people searching lyrics on google.
Other way around. It was invented to stop crawling. Indexing is still technically allowed even when blocked by robots.txt from crawling.
The problem is that Google is stealing content and placing it on search so the user never goes to the source, By blocking it with robots they block themselves from google results AND Google may already keep scraping the content.