How does one become underrated?
I guess it depends on the individual band. It could be a matter of lack of label support or lack of promotion, those have certainly happened before. Failure to land a good touring spot might be a factor as well. The wrong time could be a reason as a band could release a great metal album, but their style might not be in so they go unnoticed. The wrong place might be a factor as well because a band from a less prominent scene may not get as much of a push or attention as a band from a hot scene.