Why cannot call scss from html in ionic4?

I’m migrating source code from ionic3 to ionic4.
If I wrote the style directly in the html it can be applied, but I can’t call scss using class in html.
Why I can’t call scss from html?
It works in ionic3.


  selector: 'page-login',
  templateUrl: 'login.page.html',
  styleUrls: ['login.page.scss'],
  providers: [CustomNativeStorage]


  <div class="welcome_text">


page-login {
    margin-top: 50px;
    color: white;
    text-align: center;