Non-native English speakers? The only other translations available are in French and Polish (on MangaDex anyway) so those who know English enough to read the translation, but not understand the idioms, would need that. It's possible that a different translation would work also, but if an idiom works best for the sake of being concise, it's probably easier to just explain the idiom for the few that won't get it than to risk sounding awkward or unclear for the majority.