Because it would have had the same disastrous effect on Northern farmers as it did on Southern ones, and would have hampered the war effort.
It confirms that Lincoln was not passionately anti-slavery. Emancipation was a war measure, not principally a crusade.
Because it related to those states where Lincoln had no authority. Southern slaves were only freed when Northern troops directly robbed their owners of their property, which included slaves.
Only the slaves in the southern, seceded states. He needed the support of northern slaveholding states to win the Civil War.
Slaves in the rebelling states
Abraham Lincoln's Emancipation Proclamation was a document which symbolically freed slaves in the United States.
Abraham Lincoln signed the Emancipation Proclamation in 1863 to prevent foreign recognition of the Confederate States of America. As Lincoln had no power to free slaves in the Confederate States, the document did not free any slaves and exempted slaves in loyal Union states and in those areas of the South occupied by Federal troops.
President Lincoln waited for this victory to release the Emancipation Proclamation that freed the slaves in the Southern states (but not the Northern states).
He declared that slaves in rebellious states were free.
The Emancipation Proclamation was Lincoln's wartime act that freed slaves.
Abraham Lincoln
Freed all the slaves in the Confederate States
Abraham Lincoln wrote the Emancipation Proclamation which said that slaves in the Confederate States of America were free.
Well, the country had split. The northern states did not have slaves. The southern states wanted to have slaves. Since Jefferson Davis was their president (or was soon to be) the southerners believed that Lincoln had no power over them. Lincoln did not include the boarder states for fear they would join the Confederate States of America in protest.