Why didn’t Lincoln free all slaves in the United States?

President Lincoln issued the Emancipation Proclamation on January 1, 1863. It is correct that this proclamation did not free all of the slaves in the United States. In fact, it only freed slaves in the rebellious, Southern states. Slaves living in border states were not freed in the Emancipation Proclamation. Border states at the time included Delaware, Maryland, Missouri, and Kentucky. These states had not joined the South in the Civil War, but they had been loyal to the Union. These states were rewarded, in a sense, for their loyalty. In addition, the wording of the Emancipation Proclamation left as enslaved any slaves that had come under Northern control during the war itself. However, don't forget that the proclamation also inspired people, including whites and blacks fighting on the Union side in the Civil War. This inspiration cannot be highlighted enough.
https://www.archives.gov/exhibits/featured-documents/emancipation-proclamation