Urns are typically associated with cremation. But as a Catholic cemetery for most of its history, cremation was prohibited or discouraged by church officials. During the last 50 years, rules have been relaxed in part due to high expenses incurred from traditional burial services. Cremation has become more common, but traditional Catholics would still frown at the idea.
Remember that vaults in Recoleta Cemetery are meant to be used by families over successive generations. As the earthly remains of past generations decay over time, they can be transferred to smaller containers to make room for current family members. Although it may seem a bit gruesome, there’s no need to keep an entire casket when there are only ashes inside. Just as many caskets are traditionally draped with a cloth or shroud, so are urns.
As a decorative motif, draped urns can be found in special niches:
Or decorating the corners of family vaults:
Urns may be accompanied by an image of a woman in mourning:
They are even prominently displayed at the service entrance & on the main gate:
And as Lisandro mentioned in the comments below: “Often but not always, Christian communities during Lent use a cross with a cloth draped over its arms. This cloth is associated with the shroud of Christ left in the tomb after resurrection, & for that reason it is considered a sign of life & hope.”