In fact, even Massachusetts didn’t enact laws to outlaw slavery. They did use the courts to allow some slaves to be freed.
At the same time, many Massachusetts towns required a large bond if anyone wanted to free their slave. The towns were afraid that they would have to support those slaves and didn’t want the responsibility.
In those days you needed land to be a farmer or some skills to support yourself. The slaves had neither and relied on their servitude to keep a roof over their head.
The next time you visit Boston, just for fun, ask the tour guide in Quincy Market where the slaves were auctioned. They will choke and deny it but slaves were auctioned right near Faneuil Hall. An inconvenient truth.