Translators are not only about files, but also network, user authentication, sound stream, etc. Everything in the system actually.
For instance, on a Linux system, to use a VPN, you need to set up a tap, which is a privileged thing. With translators, since the TCP/IP stack itself is not hardwired in the kernel but translated, you can start your own stack as a translator, using a UDP stream via the main TCP/IP stack to send packets to some remote place, and then you can make your application use that translator, thus getting the VPN feature without needing privileges.