Something doesn't work as it should
This story actually starts years ago. I wanted to use lftp to transfer files to my host's server. Unfortunately, lftp seemed to just hang in there, stuck at the [Making data connection...] stage.
At that time, I frantically searched the web and I finally found a forum post that advised adding set ftp:ssl-allow off to ~/.lftprc. I did so, and I was at least able to transfer my files using lftp. Something seemed off, though. My not-yet-fully-security-aware self let it go: as long as it works...