As with linked lists, pretty much the only reasons for which you might want them are: a) If your keys are really big, copying them around may be slower than us

As with linked lists, pretty much the only reasons for which you might want them are: a) If your keys are really big, copying them around may be slower than using pointer manipulations; you'd have to benchmark this to be sure for particular cases. b) You can use use them as intrusive data structures, with one structure in multiple trees or lists at a time, and you can insert one without dynamic allocation.