It's tiny, you don't need keys, it can run any any port privileged or not with or without an install. It can take a port and pipe it to a shell, or a program, or the file system. I guess I didn't say anything the article didn't, I've mostly seen it as part of rootkits honestly. Good tools can be used for anything good or bad.

Think of *nix as Lego. You can build anything with just plain white bricks but it's fun to play with the special brightly colored ones too.

Most of the things one wants or needs to do on the net are most easily accomplished with dedicated tools, so places where only netcat will serve are rare. It comes in handy for odd corner cases, or in restricted environments where dedicated tools might not be present (it was invaluable when I was a consultant).