Because his original intent was to preserve the Union.
Why did he not include those slaves in nearby Maryland's Eastern Shore????
Because he was prohibited by the US Constitution from doing so.
-btw the number of question marks used is normally one per sentence, unless the writer is experiencing keyboard lock. If you'd care to express yourself do so directly so there is no misunderstanding.
Because the President had no constitutional right to unilaterally eliminate what had been at that time a class of property, as he was merely an executor of the law, not its author and Congress had not yet chosen to act.
However, as a war measure, he could unilaterally order the confiscation of any material which could aid the rebels under his power as commander-in-chief. Thus, he could free slaves, but only those in areas under rebel control, because those were the only ones which could have been useful to the confederacy. This is why freed blacks were often referred to as "contraband."
I find it interesting that Southern lore has it that Lincoln was a dictator, yet, at the same time, attempts to portray him as insincere for not freeing the slaves in Union-held territory with the Emancipation Proclamation. This distinction, in fact, showed a recognition of the limitations of the powers of a President.