You got one big file with code. For a game like Call of Duty, will be over a million lines of code used. You can imagine it will be a mess, if you don’t structure this well.

example

You want to change the characteristics of weapon. If there are no objects, it should mean that all code blocks exists in one file. For a game as Call of Duty, you can have over a 10,000 methods

Same as you write a encyclopedia without chapters. People will think it is an over kill of information and never read it.