Okay, brutal but awfully funny.
And yes, to be constructive, in high-density population areas, burial takes up too much real estate. Plus, people who get buried tend to go with the whole coffin routine, so the bio degrading process would take far too long to be sustainable with so many people dying all the time.
You could go with the Towers of Silence route, but according to one account I read, the vultures had a habit of dropping bits of people parts in the city-proper. I don't know that I'd want to live with hunks of dead people falling on me.
Cremation is, to me, a sensible option, after donating any usable parts. And while I realize it's entirely irrational, because I'll be dead, I don't like the idea of being in the ground. It's cold in there. I'd prefer to be warm, thanks.