But then why bother to package the game for the distro in the first place?

There‘s no reason not to use both. For some things a GUI file manager is more convenient.

Do you know what takes up the space? Something like gdu or ncdu will help you analyze the problem.

Where was that? At least the part where they force you to buy the book from their website or the college store would be illegal in the EU. (I am not a lawyer.)