Answer: To ensure the President is not lying to the people.
Explanation:
The State of the Union is a very important speech by the President and acts as an official update on the affairs of the country. As a democracy, it is important that ordinary Americans know what is going on in their country.
This is why it is important that whatever the President says is fact-checked to ensure that they are not misleading the nation on how the United States is doing. The people deserve to know the truth so that they may decide whether to keep going with the current administration or whether a change is needed.
Fact-checking the State of the Union can even be said to be a patriotic act as it ensures that the country is being fed the facts.