Why is 'return' needed when describing tasks in gulpfile.js?

Question

gulp.js

Good afternoon, why do we need 'return' when describing tasks in gulpfile.js, if everything works without it?
For example, in the description of the plugin https://www.npmjs.com/package/gulp-sass/ it says that you need to write with 'return', but in many lessons on YouTube I write without 'return', and it works like that.

gulp.task('sass', function () {
  return gulp.src('./sass/**/*.scss')
    .pipe(sass().on('error', sass.logError))
    .pipe(gulp.dest('./css'));
});

Answer 1

so prettier)

Answer 2

For the function in the task to return a value.