No, they didn't forget--they didn't want to tackle this divisive issue while in the throes of battle against a foe they'd rather not fight and didn't want to risk being divided. There are many writings of the Founders cursing slavery and King George's refusal to allow the colonies to ban it. Study your history, bub, and maybe you wouldn't support such disgusting issues like legalized child pornography.
Yeah, old Tom Jefferson was really against it. ha ha. Whether or not he had sex with Sally Hemmings, he did sell her off later in life to cover some of his debts.