They are a major thing. There are a small number of law firms.... "heavily" invested in suing ADA non-compliant websites. The run it through a online tool and if there are a certain number of errors, an intern prints out a nasty gram demanding $xx,xxx or see them in court.

These guys recently went through all the art galleries in New York City... Alphabetically. [1]

1: https://www.nytimes.com/2019/02/18/arts/design/blind-lawsuit...