Obi-Wan stopped listening in the desert. Cere shut herself off so she would not fall. Sskeer’s Magrak syndrome ate the connection from the inside. Nomi Sunrider (Legends) built a wall around Ulic. Ysalamiri (Legends) push the field back like weather. The holocron files these together so nobody thinks the saber is a permanent passport.
Quiet is not the same as gone. Kenobi came back. Some do not.