Someone still has to build and maintain the parsers, you are just outsourcing this. And I added a bit to my comment, I tend to believe that parsing is the easy part, but that is admittedly more a gut feeling and not based on any real knowledge of that problem space.
Languages usually change slowly, though, so once a good baseline grammar is in place, maintenance is unlikely to be a huge load.
Furthermore, with tools like tree-sitter and the language server protocol, multiple communities benefit from their continued existence, so there's a bigger pool of contributors to the parser.
