I understand the reasons for sending a postcard from a hospital or a school, but who would send a postcard from a cemetery? I would expect the message to read: "Just buried Uncle Bob. We would have invited you to the funeral, but the weather was hot so we had to get it done quickly."
Nope, people just used them to send regular old greetings, with no reference to the cemetery at all.
Here are two cemeteries in Pennsylvania, one in Lancaster and one in Lewisburg.
The one below looks more like a park than a cemetery from this viewpoint. Several famous major-league baseball players are buried her, including Walter Allen "Heavy' Blair, Christopher 'Big Six' Mathewson, and Harry Elwood 'Moose' McCormick.
Here are the backs of the cards in the same order.