Why remove the option to listen on an interface?

[arty-hlr]

Hi,

A few years ago I made a pull request adding some QoL features, including being able to give an interface to listen on (#13). I didn't check again until I fixed the issue of nc listening on a random port on my fork, and then noticed that there was another commit from @CrossedWires after the PR that squashed being able to give an interface to listen on (ad0ac3a).

Why remove that option? Why can't it do both? In the end that commit also checked that the IP was bound to an an interface, so why not allow giving it an interface as well as an IP?