In the USA we take it for granted that a grave site is perpetual.
In other European counties, it is common, these days, to lease the burial site for a few decades, and then have the remains removed to open up an available plot.
How American Cemeteries Promise To Keep Your Grave Forever
Yeah, we take it for granted. I'm dealing with that now with my family's graves. They're in a large cemetery. There's another cemetery across the road. Both are now owned by the same group.
When you buy a plot, the money is supposed to go into a fund that is invested by the cemetery. The proceeds of the fund are supposed to provide them with enough profit to pay for the upkeep of the cemetery and make them some profit. Unfortunately, cemeteries get bought and sold, along with the investments, and upkeep goes by the wayside as they try to maximize profits.
I've had to deal with stones getting moved around, tire tracks through the graves, perennial flowers mowed down, huge dead tree on the next plot over dropping limbs, entire cemetery not getting mowed for months, chipped gravestone from the mowers, and promises from the management to do something. Nothing happens, you call back and ask to speak to so-and-so, and are told they no longer work there because the cemetery is under new management (it got sold again). You ask why the place isn't mowed; they fired the mowing contractor and a new one doesn't start for a couple weeks.
About the only thing that gets them moving is telling them that you are to the point that you're considering digging up your whole family and moving them to another cemetery and letting all the local TV stations cover the story.
The whole thing is just disheartening.
On the other hand, there's a smaller cemetery near our house that is immaculate. Always mowed. Trash cans emptied. Trees trimmed. Really nicely cared for. What's so hard about it other than doing the right thing?