Why do regular drywall anchors fail in plaster?
Most drywall anchors are sized for thin board, while plaster over wood lath is typically about 3/4 to 7/8 inch thick, so the anchor can't open properly behind the wall. Plaster is also hard and brittle, so push-in anchors tend to crack it. Long screws into studs, or toggles made for thicker walls, hold far better.
