Do you ever notice if you press your whole hand on or just press your finger tip on a surface, which hurts more? In this example, our finger tip has less surface area, and therefore more pressure, more pain.
When we put pressure on our joints (Hips, Shoulders, Knees) our brain senses that blood circulation is being cut off and commands our body to "toss & turn" to relieve that pressure. When you relieve that pressure properly with a better mattress, you are relieving your body of this job, and instead putting the job onto your mattress. Let your mattress do this job, you've got better things to do! (..like sleep lolzzz)