How Close Is Too Close For Tombstones?

With the beautiful weather outside today in Shreveport (high of 65 and sunny) Cory's sister Casey and nephew Brock decided to take some time to visit the grave sites of some relatives.  After walking around the cemetery for a while, Brock called his mom over to see a couple of headstone markers.  His first concern was that some of the marker were extremely close to each other.  His other concern was a number of markers that were covered in dirt.  His question for all of the adults at our traditional Sunday dinner was, "why would families allow one marker to almost be o top of another"  and "Do you think the families know the markers are that close"?   I gave him the best answer I had..."Buddy, I have no idea".  What do you guys think?