Yes they do. The cemetery typically will have double vaulted plots (2 deep). When a family purchases this plot, they are purchasing it for two burials. If they purchase a double vault and decide to have cremations, they can fit several into this plot. When a cemetery is full they will purchase land adjacent to the cemetery and/or build a mausoleum on the grounds. A mausoleum can house hundreds to thousands of bodies and cremations.
There have been stories of cemeteries getting rid of old burials to resell the [plots. That is not ethical and is actually a criminal offense in most states. However, in Europe there are places that if your family does not continuously pay for the upkeep of a plot, they throw out the remains and resell it.
There is a city in northern California which is dedicated to cemeteries. It is called Colma and has more dead residence than living residence.