> because it's too much work to write migrators for every data structure change? I think that might be one factor. And writing that migration by hand would be

> because it's too much work to write migrators for every data structure change? I think that might be one factor. And writing that migration by hand would be another source of potential errors to sneak into your program without some static analysis to ensure the streams in your program are handling the version of the data specified. Making it easier to write migrators and have your whole program verified automatically has been working well for me.