为什么Composer需要jquery安装不需要的PHP包?

I just wanted jQuery and entered in the command line composer require components/jquery ^1.11

But the log shows me:

Package operations: 4 installs, 0 updates, 0 removals
  - Installing symfony/process (v3.2.7): Loading from cache
  - Installing kriswallsmith/assetic (v1.4.0): Loading from cache
  - Installing robloach/component-installer (0.2.3): Loading from cache
  - Installing components/jquery (1.11.0): Loading from cache

Why does Composer install PHP related packages I never intended to install? And how do I get rid of the unwanted packages? Is there an better/cleaner install method?

you are trying to install on of 1.11 versions of a package, which is requires "robloach/component-installer" package to install , you can see that clearly here :

"require": {
        "robloach/component-installer": "*"
},

however, robloach/component-installer requires some additional packages too, also you can see that here

"require": {
        "php": ">=5.3.2",
        "kriswallsmith/assetic": "1.*",
        "composer-plugin-api": "^1.0"
},