What cases are you thinking of? I don’t think I’ve read those, or if I did, it was under a different heading.
Let’s be plaintiff’s lawyers: if I wanted to sue B for negligence I would argue that B had a duty of care towards A, that B knew that A was likely to be hurt and deliberately behaved in such a way as to make that more likely to happen DESPITE knowing that no harm to B would come from taking the hit.
Or something like that. I don’t think it’s a meritorious case, I don’t even think it survives a 12(b)(6), but there’s no need to be this way, and there’s no need to condescend just because you’re used to doing the analysis differently. For the record, if it’s stipulated in the problem that C has impleaded B, I don’t think you would get very far by arguing in conclusory fashion that OBVIOUSLY nobody could ever find B’s conduct negligent.