It's a little bit like asking what's the use of a linked list. A map which can iterate through keys in insertion order is just a data structure.
A recent use-case for me was using timestamps as keys that map to captured state at that time.
Well, no, it's more like asking why you'd use data structure X instead of Y.
I was asking why you'd want that property as part of your data structure, and pointing out that (AFAIR) I've never needed it.
For your use case, I guess you wanted to be able to retrieve the data for specific time stamps? Otherwise I'd think you'd just put it into an array.
That sounds like sorted key order would suffice just fine.
It's a little bit like asking what's the use of a linked list. A map which can iterate through keys in insertion order is just a data structure.
A recent use-case for me was using timestamps as keys that map to captured state at that time.