The first issue is that ashes don’t go anywhere - staying as they are in the ground, whether that be interned or scattered on lawns, or interred as whole; staying as they are for generations. The second issue is that the ground will start to deteriorate - scarred grass on lawns, plants dying off the memorial, and a high level of replacement plants - all of which are caused by cremated remains. These negative properties, or ‘prohibitors', include the pH of cremated remains - being a very alkaline, corrosive material - especially when water passes through, and the huge amounts of sodium - around 2,000 times the tolerance of native plants. The third of these, which isn’t as much of a prohibitor, but is in those circumstances, is that after cremation, all of the biology that would assist the decomposition of bone fragments into the ground so that they could be absorbed, has been sterilized. Once those ashes are then placed in the ground, they create issues with the surrounding microfauna, breaking down the function of the soil and leading to issues with grounds.