Because you can't guarantee that everything (or even anything) in the source was actually applied. Whether it's because there was some error in doing so or beca

Because you can't guarantee that everything (or even anything) in the source was actually applied. Whether it's because there was some error in doing so or because there just was no run. Additional potential issues: how are you generating your primary keys before resource creation? Probably by some hashing of attributes known at creation time? And how are you avoiding collisions? How are you dealing with modules that may have gone through multiple commits/versions since the last time you ran an apply? There's just too many places where you really want to have a mapping of at least logical IDs -> physical IDs to ensure consistency. The one big advantage CloudFormation has here is that it just handles the state for you, but there's definitely still state.