The president’s oath of office is a simple but solemn statement accepting the obligation to faithfully fulfill his duties. Because the office carries great responsibility it's proper to begin with such a solemn promise.
However, anyone who claims to speak for God has an even greater, more solemn, responsibility. After all the U.S. President was only chosen by voters, but the prophet of God is chosen by God. Notice how God made it clear that He selects His prophets and tells them what to say (18.15" class="scriptRef">Deuteronomy 18:15, 18). There have been millions of government officials throughout history; the U.S. has had 45 Presidents. But in the history of the world relatively few have been entrusted with the work of a prophet, though many have falsely claimed the authority (Matthew 24:11).
What does God say about how we should react to prophets: true and false? First notice that the false prophet doesn't speak for God, and will answer to Him, so we must reject him (Deuteronomy 18:20, 22). Second, we are obligated to listen to the true prophet. If we do not, we will answer to God (Deuteronomy 18:19). This simple concept permeates God's word - listen and obey. Even though the presidential oath of office is short, it's still binding. The simple duty to hear and obey God's prophet is even more solemn and binding (Hebrews 2:1-3). Maybe that's why so few do.