When a man with wide shoulders lies on his side, those shoulders hold the body off the mattress. A pillow's only job is to fill that gap so the neck stays level.
Here's the part nobody explains: a normal pillow gives about 3-4 inches of height. Wider builds need 5-7. So the head drops into a 2-3 inch gap every night and the neck bends for hours. 💡
That's why stacking never held and adjustable ones went flat. It was never about comfort. It was a measurement for the frame, and no pillow ever took it.