Hey, sweetie... I ain't the one cutting up corpses and
boxing them up for posterity and tourist traps.
The reason incorruptibles are put on display is simply due to the fact that they are INCORRUPTIBLE. It is an anomaly that Christians have taken note of. Some saints have particular body parts that did not corrupt as in indication of the particular heroic virtue that they embodied.
St. John Vianney’s heart did not corrupt (I’ve seen it). St. Joan of Arc’s heart was found in the ashes incorrupt. Saint John Nepomucene’s tongue was found incorrupt because he would not violate the great seal of confession. There are many other examples.