> Because a locale-sensitive sort isn't necessarily stable.

Many implementations of quicksort aren't stable either -- or even deterministic -- but that hasn't stopped anyone. You can add an index field to force stability if that's desired.

> A locale-sensitive sort would change the output as soon as your locale changed.

Often that's the point. If I know a user speaks Norwegian, either through their preferences or Content-Language, I'd like what they see to be sorted in an order they're familiar with.

If I don't know, well, better an ordering than no ordering.