Catholics take care to honor and bury the dead because St. Paul tells us that we are temples of the Holy Spirit, that God lives in our very bodies and therefore we should honor God with them (1 Corinthians 6:19-20). Honoring the body doesn't stop after the person has died.
In Mass we profess our belief in the Resurrection of the body when we say the Creed, 'We look for the resurrection of the dead, and the life of the world to come.' Just as Jesus' body was raised and ascended into heaven so we believe our bodies will be returned to us when Jesus returns.
Burying the bodies of the dead reminds us of this hope we have in the Resurrection. It anticipates the reuniting of our body with our soul in heaven. Burial is not simply a disposing of the body but it is caring for that person to the point that it is even a corporal work of mercy to bury the dead (CCC 2300).
Our bodies are not simply shells that can be tossed aside, though our body and soul separate at death the body still belongs to that person and it will be returned to them.
That doesn’t mean that we’ll have zombie bodies that are disgusting and decaying but we’ll have glorified bodies. We'll be able to walk through walls, run as fast and jump as high as we want! The best part is, our glorified bodies won't be able to feel any pain or inconvenience!
If Catholics want to be cremated, that’s fine so long as you still have a Catholic burial of the remains and as long you aren't denying belief in the resurrection of the body (CCC 2301).