Underpowered negative results are a class of potentially genuinely uninteresting results.

Interestingly, underpowered positive results are likely to be published, but unreproducible. That is, the ratio of false positives will be higher among underpowered studies. So, the literature of underpowered studies will be enriched for false positives.

So, underpowered results, whether positive or negative, are less interesting.