> I think FTP is being kept-alive only by legacy fintech (doesn’t the US ACH depend on banks exchanging CSV or TSV files over FTP?) and low-end shared webhosting services that are too afraid to offer SSH to their customers.

FTPS is still used in mainframe and minicomputer systems as well. This is because FTP has native support for transferring record-oriented files – STRU R and MODE B/C. Those features are generally not implemented by FTP clients or servers on Linux/macOS/Unix/Windows/etc. Unlike FTP, SFTP does not have native support for record-oriented file transfer.

I understand that GridFTP is still used in high-performance computing applications. GridFTP extends FTP with features such as parallel data transfers targeted at transferring massive data sets (terabytes, even petabytes in size) over very high bandwidth links. (Aspera performs better but is proprietary; GridFTP is an open standard with open source implementations.)