Satellites are harder to predict
The exact time the satellite begins its reentry depends on many factors, but mostly the density of the atmosphere where it is orbiting. Because of heating from solar radiation the atmosphere's density changes over periods of hours and days which can dramatically change the amount of drag being experienced by the satellite.
Added to which this satellite has probably lost all attitude control so it will be tumbling and experiencing variable amounts of drag, all of which make predictions a bit less - well - predictable.
An asteroid on the other hand approaches the Earth through a vacuum at a relative speed of several to tens of kilometres per second following the laws of Mr. Newton. The atmosphere only has any effect on it during the last few seconds before it carves out a dent on the surface.