Uncover the mystery of ancient hanging coffins. Why should the coffin be placed on the cliff?

Ancient science and technology were very underdeveloped, and it was necessary to place hanging coffins weighing hundreds of kilograms or even more on the cliff. It was a test for ancient people, and the amount of work was huge, some even hundreds of meters from the ground. It's difficult to dig holes in the cliff and place cross-bar supports, and make sure they don't break all year round.