How is it fucked up? The person is dead.
The body then is partly cut so that the birds can better get everywhere. Neither fire nor earth have been tarnished with the sinful flesh (important in Zoroastrianism and Manichaeism) and it's assured that it nurtures nature once more (cyclic stuff - important in Hinduism and most schools of Buddhism), furthermore the body is on a good way off to the everblue sky that way (important to Tengriism).