Why does a promise call the next then if the previous one doesn't return anything?

Question

JavaScript

Hello. Can you please tell me why the promise is called, which follows after the promise of the user.get function, if the latter does not return anything?

var user = {
  get: function() {
    return new Promise(function(resolve, reject) {
      setTimeout(resolve, 1000);
    });
  },
  set: function() {
    return new Promise(function(resolve, reject) {
      setTimeout(resolve, 2000);
    });
  }
};

user.get().then(function() {
  console.log(new Date(), "get");
}).then(function() {
  console.log(new Date(), "set");
});

Answer 1

because that's how the chick's then call works:
it goes all the
way, and it doesn't matter if you return a promise (or whatever) or not
such a construction will first print "hello world", and then "undefined", because in the 2nd then we did not pass anything

Answer 2

resolve is called on the first promise and that's enough.