CORDOVA_PLUGINS environment variable empty in hook

Here are the steps to reproduce the bug:

cordova create Baz
cd Baz
mkdir hooks/before_prepare
echo '#!/usr/bin/env node
console.log("CORDOVA_PLUGINS: " + process.env.CORDOVA_PLUGINS);' > hooks/before_prepare/1_env_plugins.js
chmod +x hooks/before_prepare/1_env_plugins.js
cordova platform add android
cordova plugins add org.apache.cordova.network-information
cordova plugins ls
cordova prepare --verbose
cordova plugins ls

In a new project, with an Android platform (the same happens with iOS), if you try to access the CORDOVA_PLUGINS environment variable as done in the 1_env_plugins.js hook, it does contains the plugins list as the command 'cordova plugins ls' does.