Perl has had this for decades. C’s strcmp() has similar semantics. I thought the motivation was that sort can be more efficient when each comparison can return

Perl has had this for decades. C’s strcmp() has similar semantics. I thought the motivation was that sort can be more efficient when each comparison can return more information (the standard library already has a sort function that relies only on using less-than operations). But people eventually realized that certain operations have to be implemented together to make sense. For instance, the sort function that relies only on less-than operations defines two values as equal if neither value is less than the other. Many people consider this weird, and wonder why sort doesn’t require both less-than and equality operations. The spaceship operator essentially implements a group of operations, and guarantees they’ll be consistent: less-than, equal, and greater-than (plus not-equal, less-than-or-equal, and greater-than-or-equal). Personally, I’m not thrilled about a special purpose solution to a single example of a problem (use this one operator to implement this group of related operations), but I do see some value in making it easy to implement this group of related operations.