you save the game. you drive around and then get killed. you reload the game. 99% of the game is the same as it was before. shouldn't you just update the game?
maybe not. if you can do all of the work required to serialize something quickly, then why can't you do all of the work to unserialize? the main reason could be loading in all that data.
however, just because you throw away your entities does not mean that you have to throw away all of your data. the data is a resource.