Why doesn't netcat bind to all interfaces on Mac OSX?

which nc
/usr/bin/nc

In one terminal window:

nc -l 1234

In another terminal window:

nc 127.0.0.1 1234

Does not connect. But when I use the IP of en0 then it works, e.g.

nc 192.168.1.42

This exact same series of commands works on my Arch Linux box (actually, both do, as well ass nc localhost 1234).

Why doesn't this work on Mac, and how do I get it to listen on all interfaces?