What is the main reason that active citizens need to understand governmental organizations? The president is the chief executive of the nation, so you can’t write to him or her whenever you feel like it.
There are websites for each branch of government, and it’s hard to read all that information.
The Supreme Court is the nation’s highest court, and you might want to take a case to those justices someday.
The government has many branches, departments, and agencies, and you need to know where to get help as needed.