I mean, do they actually expect species to stop resisting after they've heard that message? And as the borg are all about efficiency, why waste time with such a message? How many species would there have been in the past that after hearing that message, shrugged their shoulders and said: "ah, well. we suppose it's all over then, you can come in. Oh, would you please be so kind to use some anesthetic during the amputation of limbs and puncturing / gouging out of eyes parts of the process?" Or is the idea just to demotivate said species so that they put up less of a fight and there are less drone casualties at the end?