This is why you have never seen FTPS in the wild, from the vsftpd.conf manual page:
ssl_enable
If enabled, and vsftpd was compiled against OpenSSL, vsftpd will
support secure connections via SSL. This applies to the control
connection (including login) and also data connections. You'll
need a client with SSL support too. NOTE!! Beware enabling this
option. Only enable it if you need it. vsftpd can make no guar‐
antees about the security of the OpenSSL libraries. By enabling
this option, you are declaring that you trust the security of
your installed OpenSSL library.
Default: NO