Hi,
You are right. The reason for the parent game object is to keep our Hierarchy tidy. In a little game like ours, it probably does not matter that much how we organise our project.
However, it is usually advisable to start with a good structure that allows us to expand our game at a later juncture. When developing a game or another project, we always want to keep our future self in mind. What if we decide to implement more ideas? Do we get chaos, which is another problem we would have to solve? Or should we invest a couple of seconds to implement a good structure which will (hopefully) prevent chaos?
Long story short, our parent game object is “good practice”. If you have another solution to prevent potential chaos in the Hierarchy, that’s perfectly fine, too. 
Did this answer your question?
See also:
- Forum User Guides : How to mark a topic as solved