Why does npm install download so many dependencies?

Question

Layout

I use NPM to install packages from gulp.
When executing the npm install command, about a hundred folders are installed in the node_modules folder, as a result, 3.5 thousand files are stored in node_modules , despite the fact that I install only gulp and its packages.
Is that how it's supposed to be or am I doing something wrong?
My package.json:

{
  "name": "",
  "version": "1.0.0",
  "description": "",
  "license": "ISC",
  "devDependencies": {
    "gulp": "^3.9.0",
    "gulp-autoprefixer": "^3.1.0",
    "gulp-concat-css": "^2.2.0",
    "gulp-cssnano": "^2.1.0",
    "gulp-notify": "^2.2.0",
    "gulp-rename": "^1.2.2",
    "gulp-scss": "^1.3.17",
    "scss": "^0.2.4"
  }
}

Answer 1

That's fine, everything else is dependencies and dependencies of dependencies.