What do you gain by hiding the body? In some cases, it may be possible to hide the fact that any crime was committed. If a globe-trotting reporter were murdered in London and the body never found, then that reporter might just be regarded as missing in action anywhere around the world. But that was impossible in the case of Chandra Levy.
As an intern whose term was up at a particular time, and whose parents were expecting her back in California shortly afterwards, Chandra Levy's disappearance was bound to be noticed, whether a body turned up or not. With the passage of time, the likelihood of an accident would have to decline to the vanishing point and foul play left as the only reasonable conclusion.
If her death was caused by someone who knew her, then that person would also know this. Thus there would be no point in trying to conceal the very existence of a crime. All that could be concealed would be the identity of whoever was responsible. Misleading the police about the time at which her abduction happened might be worth spending some time at her computer or having someone else spend time there.
In any event, someone obviously thought it was very important that her body not be found. But why? If her body were found in a park or on the street with a fatal gunshot wound, for example, how much of a clue would that be? Enough to take the risks of spending time finding a secure place to dispose of her remains?
What would make her body a bigger clue would be if she were pregnant. That could point the police toward whoever was responsible for her death. Moreover, pregnancy could have set in motion a chain of events that led someone to feel a need to get rid of her permanently. Pregnant young women can cause big trouble, especially if they feel betrayed by whoever was responsible.