That fact is parsed to death by south haters here
Why did Lincoln not free slaves under his control?
I guess cause he didn’t want to deal with them
Who would feed them etc
They ideally hoped they would all stay down south once freed and negate any political power of the rebels and become totally dependent on their new federal masters
Kind of how it turned out in the end now
Just the political parties changed coats
He did not free the slaves in the 4 slave states that remained in the Union because he did not have the Constitutional authority to do so. The Dred Scott Decision of 1857 specifically stated that the Federal Government could not interfere with the institution of slaver in any state where it was legal. Lincoln spent a considerable amount of time trying to get Missouri, Kentucky, Maryland and Delaware to abolish slavery but he had no authority to order that action.