Status effects inflict the victim with negative keywords. As opposed to the tens of marks and poisons out there that each differ in the keywords they carry, there are only a handful of status effects, and the same status effect will behave pretty much the same no matter what skill carries it. Since a specific status effect is more common than a specific poison, it's more important to understand a copy may only suffer from one copy of a specific status effect (or specific mark or specific poison), so reapplying it will effectively only reset the keyword, not double it.