Why is gulp.watch taking a long time to start?

Question

JavaScript

There is this code:

gulp.task("watchLibraries", function(){

  //For JS
  gulp.watch(["assets/js/libraries/**/*.js", "!**/*.min.js"]).on("change", function(event){
    compileJs(event.path); //Сжимает js-код
  });

  //For CSS
  gulp.watch(["assets/js/libraries/**/*.css", "!**/*.min.css"]).on("change", function(event){
    compileCss(event.path); //Сжимает CSS код
  });

});

I call a task.
gulp watchLibraries
And I get something like this:

Why does watch take so long to start? 20 - 150 seconds? There are 30 files to be monitored. What could be the matter? I'm most likely misunderstanding how chokidar works...