Comment by bluecalm

The main thing is that he object can be a member of various structures. It can be in big general queue and in priority queue for example. Once you find it and deal with it you can remove it from both without needing to search for it.

Same story for games where it can be in the list of all objects and in the list of objects that might be attacked. Once it's killed you can remove it from all lists without searching for it in every single one.