[harrall]

Less than 1% of the hash maps I use have ever needed order.

The underlying data structures between both are different. Ordered hash maps use more memory, are slower, and are more complicated.

Knowing CS fundamentals, using an ordered hash map should be a deliberate choice like renting a box truck when you need to move a lot of stuff. Don’t just drive a box truck everywhere because you might pick up a couch from a thrift store one day.

[btschaegg]

All well and true if all you have to do is process the data programmatically.

And yet, as I said, if the same thinking gets applied to e.g. a store of JSON documents (like ELK), chances are good the thing will ruin the UX for countless people who have to deal with the result. Note that you need exactly no hash maps to store the JSON as it is text.

To expand your analogy: …and yet roads are built so that you can drive your regular car or a box car over them, depending on your use case. You make the choice. A JSON library that doesn't afford such choices (and isn't hyper focused on performance) isn't a good one in my book.

Edit: As a sidenote: Or do you mean a freight train wagon? Then replace "road" with "rails" and "car" with "draisine" :)