Yes they are very important in my opinion, my parents headstone is a piece of stone that was imported from Tibet, no idea why but it is,. but anyway, purely from a family historians point of view they provide a unique source of relationship information that is just not available anywhere else, my great grandfathers grave in St Thomas's gravetard Stockton Heath lists 8 occupants, their relationship and their dates of birth and death, no where else does that kind of generational audit occur,
The erection of a stone or memorial began when people were buried within the church rather than outside, and their names were carved on the paving stones that the congregation walked on, merely to inform and not duplicate burials. The further away from the alter a burial was the less important a person was in their village. When the ground beneath the church filled, bodies were dug up and burnt (hence bonefire/bonfire) and space freed up. Then people started being buried outside but the local pigs could dig them up so they started burying the bodies 6ft deep and then buily a wall round the churchyard to keep the pigs out.