FTP

• Directory listings are the output of "ls". Have you ever tried having files owned by users or groups with spaces in them? Say… "Domain Users". Clients fall flat on their face trying to parse the output as they have to split fields by whitespace, which obviously fails with such user & group names.
• FTPS is even more broken (assuming you mean encrypting the control connection, too, not just the data connection). With FTPS you can only use the passive mode, and your server must not be behind any kind of NAT. Why? Because no firewall device can parse the encrypted control connection & can therefore not determine the dynamically-allocated port numbers the server & client use.

Sure, you can use it in certain circumstances, but it's not a general-purpose solution.