Reasons I can think for dedicated graphical clients is the transfer log and the additional controls when connecting to servers. I agree that it's not really necessary unless you have very specific requirements, I guess.
[1]: https://support.apple.com/guide/mac-help/network-address-for...
I do agree that most of people only use FTP for that, so I guess it's sufficient for average user. Protocol support would still be an issue though.
Windows used to do it through Internet Explorer, and it was very easy to screw up your whole desktop session as soon as there was anything slightly wrong with an FTP connection. It also did not support ftps or sftp, and often would not handle write permissions properly. I’ve not checked recently but if i remember correctly, years ago there were reports that Microsoft would (rightly) remove support at some point (ftp is just a bad and insecure protocol in 2021).
MacOS Finder afaik never had write-permission support for ftp, and overall the experience was similarly poor. I used to run Cyberduck or Transmit if forced to use FTP.
Linux desktops did include decent support for FTP, particularly in KDE Konqueror which had a great plugin architecture; I expect they still do. FileZilla was never popular on Linux anyway.
It can save multiple accounts within the same site, have different IPs and auto rotate, have different profiles about speed limit, thread limit, listing method, encodings, default folder to open on both sides, to name a few.
Cyber duck for me !