Why is it necessary to call the EventEmitter class when creating a new event listener in Node.js?

var EventEmitter = require("events").EventEmitter;
var https = require("https");
var http = require("http");
var util = require("util");

/**
 * An EventEmitter to get a Treehouse students profile.
 * @param username
 * @constructor
 */
function Profile(username) {

EventEmitter.call(this);

profileEmitter = this;

//Connect to the API URL (https://teamtreehouse.com/username.json)
var request = https.get("https://teamtreehouse.com/" + username + ".json", function(response) {
    var body = "";

    if (response.statusCode !== 200) {
        request.abort();
        //Status Code Error
        profileEmitter.emit("error", new Error("There was an error getting the profile for " + username + ". (" + http.STATUS_CODES[response.statusCode] + ")"));
    }

    //Read the data
    response.on('data', function (chunk) {
        body += chunk;
        profileEmitter.emit("data", chunk);
    });

    response.on('end', function () {
        if(response.statusCode === 200) {
            try {
                //Parse the data
                var profile = JSON.parse(body);
                profileEmitter.emit("end", profile);
            } catch (error) {
                profileEmitter.emit("error", error);
            }
        }
    }).on("error", function(error){
        profileEmitter.emit("error", error);
    });
});
}

util.inherits( Profile, EventEmitter );

module.exports = Profile;