Kelly -

You don't have to bury them. I personally like it that my villagers do because the little corpses are kind of scary looking . If you don't have the proper tech levels to bury them they will decompose after 24 hours anyway, and they'll do no harm laying there. Unless of course you have a village of fragile people who might become depressed looking at corpses all day. Of course this might also motivate them to work harder and not wind up as a corpse themselves. One never knows with these crazy villagers!