the script installs Docker for the root user (instead of doing it for a specific group with particular permissions)
it installs everything (plugins, the command-line, …) whereas in a production environment you only want what’s necessary
it installs the latest version and does not allow for updates. On a production system, you prefer to manage updates manually and know which version to install.
For our purposes, the script is more than sufficient.
A quick apt-get upgrade (or other package manager) will update it.