What to do if .css is missing in "main" in bower.json (when working with bower + wiredep)?

Question

Building projects

I use gulp, bower + wiredep:

<!-- bower:css -->
...
<!-- endbower -->

But often when connecting a plugin, for example FontAwesome, in bower.json in "main" there is no path to .css, but there are paths for .less or .scss

"less/font-awesome.scss"
"sass/font-awesome.sass"

If you write pens there,
"css/font-awesome.css"
then wiredep, of course, connects this .css to html
. But I, in my opinion, do not use wiredep for this.
Am I doing something wrong? How to solve this problem? Or is there no solution, to connect unconnected files yourself?
gulpfile.js

var gulp       = require('gulp');
   concatCSS   = require('gulp-concat-css');
   minifyCSS   = require('gulp-minify-css');
   rename      = require('gulp-rename');
   prefix      = require('gulp-autoprefixer');
   sass        = require('gulp-sass');
   uncss       = require('gulp-uncss');
   wiredep     = require('wiredep').stream;
   browserSync = require('browser-sync').create();
   reload      = browserSync.reload;

gulp.task('default', function() {
  return gulp.src('sass/*.sass')
    .pipe(sass())
  	/*.pipe(concatCSS("bundle.css"))
  	.pipe(prefix("last 30 versions"))
  	.pipe(minifyCSS(""))
  	.pipe(rename("bundle.min.css"))
  	.pipe(uncss({
  		html: ['index.html']
  	}))*/
  	.pipe(gulp.dest('app/'));
});

gulp.task('browser-sync', function() {
    browserSync.init({
        server: {
            baseDir: "./app"
        }
    });
    gulp.watch("app/*.html").on("change", browserSync.reload);
    gulp.watch('sass/*.sass', ['default'])
    gulp.watch("app/*.css").on("change", browserSync.reload);
});

gulp.task('bower', function () {
  gulp.src('./app/index.html')
    .pipe(wiredep({
      directory: 'app/libs'
    }))
    .pipe(gulp.dest('./app'));
})


gulp.task('watch', function () {
  gulp.watch('bower.json', ['bower'])
})

Answer 1

I would like the gulp.js code to the studio.
For example, wiredep works for me only at the time of bower install, but everything depends on the settings.