There are many “unwritten customs” that affect the way that government is conducted but which are not explicitly written into the Constitution. Let us look at two of them.
The cabinet. The cabinet as a group is not mentioned anywhere in the Constitution. Even so, cabinets have been important parts of government. Presidents have used cabinet meetings as forums for testing ideas and getting advice. This came about without being part of the Constitution. It is also worth pointing out that this custom is gradually losing its status as a custom. Cabinet meetings are becoming less and less important. This change, too, is occurring without any formal change in the law.
The State of the Union Address. This event is mentioned only very briefly in the Constitution and is not described in detail. Early presidents did not even give an actual speech but instead sent a written message to Congress. Because of custom, however, this has become an important event each year. It is seen as a way for the president to get his (or someday her) agenda out in front of the people.
Thus, we can see that unwritten customs have had a major impact on how the president’s agenda is transmitted to the Congress and the people and on how the president receives advice on policy issues.