Why do Christians bury their dead when the Bible does not command burial?

Christians generally bury their dead in a sleep-like position to symbolize their belief that the deceased is merely sleeping while waiting for resurrection.

1 Corinthians 15:51Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed,

52In a moment, in the twinkling of an eye, at the last trump: for the Trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.

Answer:

There is a certain natural sentimentality connected with our dead loved ones, which dictates that we honor them with respect and in peaceful burial if possible. Yet, a fair share of Christians were burned at the stake, and a whole varitety of imaginative ways, which left precious little to "lay out" in a coffin.

Even Abraham went to certain involved extremes to bury his beloved Sarah (Gen.23).

But the main reason to bury the dead is the same for Christians or anyone else. It's to prevent the spread of disease... the fear of which was one of the concerns with the bloated bodies left by the tsunami in Indonesia. The same fear was extant in New Orleans. The same goes for the decomposing bodies in the wake of war. Disease is one of the natural results of war... which are two of the "four horsemen of the Apocalypse," which are ongoing and integral components of sinning man's life on earth.

Burial of the dead isn't a sentimental religious exercise... it's practical and necessary.