Why do Muslims bury within 24 Hours of death?

Muslims believe in keeping the body as close as possible to its natural state. Unless there are extenuating circumstances, the body is not embalmed, frozen
 or autopsied.

It is also because Islam began in a really hot climate where the spread of disease was a very real peril and bodies decayed fast. The best way to make sure dead bodies don't spread disease in such climates is simply to bury them fast. This also keeps the dignity of the person.

Muslims feel the world as temporary place, when soul leaves the body there is no reason to keep the body and real life begin after death.

Many Islamic States have their own customs and laws regarding burial. 

Jews also bury their dead within 24 hours.