No one really knows why the ancient Egyptians began to think that preserving their bodies was important. Although soon after they began preserving bodies they believed that if a person's body was not mummified they would not live in the next world.
One of the most important documents in early Ancient Egypt is the Pyramid Text. It was a group of spells and instructions which were thought to help the deceased make the transformation from death to resurrection.
In a tomb there is always a storage room. In the storage room are all kinds of things that might be useful in the next life: furniture, hunting equipment, sealed jars filled with oils, wines and beers, cosmetic items, and games.
Basically, the while point of the tombs was to establish a life after death that was very similar to life on earth. The Egyptians worked hard to make completely sure their loved ones were happy and comfortable.
Soon, however, every day useful items in the tombs were not enough. Egyptians began to include symbolic items like models of people or things. Even the poor had many items in their burial tombs.