It boils down to a belief in the goodness of the body and the resurrection of the dead.
In general, the body is honoured by being kept together and not by being discarded as something with which we are done. Placing it to rest to await the resurrection is appropriate. There is recognition that most bodies of the dead will in the end need to be reconstituted, but that of itself is not the way it was meant to be.
If a particular person who has gone on to their heavenly reward is very active in the consciousness of the Church, it may be appropriate to honour them and recognize the eventual glorification of their body by spreading their body, even in its unglorified state, around, provided that it continues to be honoured. I wouldn’t want to have the bodies of my great-grandparents with me, even though I honour them in a way.
On the other hand, sitting about three feet away from me at this moment are small bone fragments from St. Thomas Aquinas, St. Augustine, and St. Monica in one small reliquary, and fragments from St. Philip Neri, St. Lawerence of Brindisi, and St. Jerome (Hieronymus in Latin) in a second. They are important spiritual patrons for me, intercessors, and friends. I believe on the last day the fragments will end up in their proper places and be glorified. In the mean time, these six saints in heaven think of me much more and more effectively than I think of them—though I do think of them, and strive to imitate Christ as they imitated Christ.
For those of you unfamiliar with the Saints, Aquinas and Augustine are the greatest theologians in the Church, Monica was Augustine’s mother and a huge spiritual warrior, Lawrence B and Jerome are the two doctors of the Church who are the greatest specialists in Scripture, and Philip Neri is another huge spiritual warrior, who in various ways is tied into St. Jerome. Given my own profession and my own personal life, these are awesome examples for me on how to imitate Christ.
In-deed:
The Order of the Good Death The (Not Really So Very) Incorrupt Corpses
[some] incorruptibles get treatments (like a corpse spa) and it’s no big secret.
According to Church doctrine, incorruptibility alone can’t be counted as a miracle anymore. More sophisticated scientific explanations as well as mistakes found in hundreds of years of preservation records have forced the Church to reconsider which saints deserved the title in the first place....
small differences in temperature, moisture, and construction techniques lead to some tombs producing naturally preserved bodies while others in the same church didn’t....
Once the incorrupt bodies were removed from these climates or if the climates changed, they deteriorated. This may have been what happened to St. Francesca Romana who was deemed incorrupt four months after her death in 1440 only to be found fully skeletonized in 1698 (though you still hear people refer to her as incorrupt)...
The use of wax as an artist’s medium invites even more confusion and misunderstanding when it comes to the incorrupt. There are thousands of wax effigies in Catholic churches. Some have relics inside them, others don’t, and maybe a few hundred are fully incorrupt corpses wearing wax masks.
At the turn of the 21st century, the Vatican commissioned a team of pathologists and chemists to study saints’ bodies. The team encountered many cases in which saints had clearly been mummified, often by their followers, in an attempt to preserve (or help preserve) their bodies. One of these cases was Saint Margaret of Cortona. - https://psmag.com/environment/incorruptible-bodies-saints-religion-catholicism-pope-john-paul-94892<
The Incorruptibles The bodies of many medieval Catholic saints and martyrs have resisted decay for centuries— just the sort of mystery that begs for scientific inquiry By Heather Pringle -
Those who preserved Saint Margaret had done so remarkably thoroughly, excising her internal organs and drenching her skin in fragrant lotions. Their handiwork reminded Fulcheri of the techniques employed by ancient Egyptian embalmers. Mulling this over, the pathologist wondered whether the resemblances were merely coincidental or whether at some point in the distant past,...
In 1697, for example, an Italian surgeon left a list of 27 powdered herbs and drugs that he had employed to preserve the body of Saint Gregorio Barbarigo. ...
The church records offered no explanation for such drastic actions, so Fulcheri began hunting elsewhere for clues, searching to see if he could find other similarly mummified saints in Italy. His research has turned up five other similar cases— Saint Clare of Montefalco, Blessed Margaret of Metola, Saint Catherine of Siena, Saint Bernardine of Siena, and Saint Rita of Cascia...
By the time holy figures were exhumed during beatification or canonization trials, the tombs' microclimate had sometimes desiccated their flesh, turning it to the texture of old leather. And if there was any confusion among officials about which body was the correct one, they picked the best preserved, for incorruptibility was taken as a sign of holiness. Is it true that the bodies of some saints are incorruptible? /p>
I read _Scent_ by Annick LeGuerer some years ago and it had a section on the scent of sanctity. It discussed the presence of acetone in the blood as responsible for that agreeable floral odor described as "sanctified." Acetone in the blood is a result of diabetes. The diabetic body makes it in abnormal mass quantities. (This finding is what led to the Church saying that the incorruptible body could no longer be the only test of sanctity.) The book said St. Teresa of Avila was a confirmed diabetic (but I haven't read that info anywhere else). The book also went into how the mind (in ecstatic state) could change the blood alcohol composition so that was another way for saints to have the scent of sanctity. It was really interesting to think that our incorruptibles/saints were diabetics. - Miss P
Vatican’s secret, and deadly, project to mummify saints
Paramahansa Yogananda As reported in Time Magazine on 4 August 1952, Harry T. Rowe, Los Angeles Mortuary Director of the Forest Lawn Memorial Park in Glendale, California, where Yogananda's body was received, embalmed and interred,[46] wrote in a notarized letter[7] The absence of any visual signs of decay in the dead body of Paramahansa Yogananda offers the most extraordinary case in our experience... No physical disintegration was visible in his body even twenty days after death... No indication of mold was visible on his skin, and no visible drying up took place in the bodily tissues. This state of perfect preservation of a body is, so far as we know from mortuary annals, an unparalleled one... No odor of decay emanated from his body at any time...[47][48]
[Buddhist] Monk's Body Miraculously Intact 80 Years After Death