According to the media, on Tuesday; he will deliver an "Address to the Congress," not a "State of the Union." The semantics of word choice is very important. I believe the reason is due to him not wanting to discuss the improved economy, positive sociopolitical reforms, or a strong global standing inherited from the previous administration. Since January 20, 2017, all of those factors have declined. Also, it is because he is unable to measure up. The bar was set too high.
According to Article II Section 3, Clause 1 of the Constitution, "The President “shall from time to time give to the Congress Information of the State of the Union, and recommend to their Consideration such measures as he shall judge necessary and expedient.” The change of words implies his regard for the Constitution. Let's not be fooled.