No rational person would willingly become a hero. A hero is someone who accepts the fact that they will be blamed for inevitable loss of life. They will be the direct cause of some deaths, even if those deaths were caused whilst trying to prevent other deaths. The stronger they are, the more easily involuntary kills may occur.
If they get too good, people will blame them whenever they don't show up. Situations suddenly are phrased as "would have been preventable if they were there" and "why would they let that happen?"