If the faithful *must * be buried, why are the in-corrupt bodies of the saints exposed to the world?
The difference lies in the purpose. We generally bury the dead as a sign of respect for the bodies of the dead and a sign of our hope in the resurrection.
When individuals are not buried the reasons are usually non-Christian. And there is always the danger that over time the remains will be irreverently discarded by a future generation.
The incorrupt body of a saint is already being reverently kept even when on display. The saint can be considered to simply be “entombed” in a more public manner. But the reason for this “public entombment” is to give glory to God and express our hope in the resurrection. Everything about the situation is entirely Christian and is focused on giving glory to God.