FTP (and SFTP) is very heavily used in enterprise software, especially when two pieces of software are being integrated.

(S)FTP support has been baked into huge ERP systems like Oracle and SAP for years (I would be very surprised if BitTorrent was even on a list of development features), and when you're working with a company who has a $100mm SAP installation, you transfer files using (S)FTP.

I just finished a large integration with SAP where all of the data was transferred using files over SFTP. We have a modern REST API they could use as well, but that would've added a lot longer time to the integration as it wasn't already baked into SAP (plus, moving large files over HTTP is not ideal).