Doesthedogdie literally has about 100 different categories (more than even the letters of the alphabet). Analysis Paralysis is a thing. That’s why we don’t want to balloon it. It’s also why movies don’t target specific ages on their ratings already, but a range of ages. Too many options means less familiarity with the system and information overload.
I know a lot of people who are more upset by knives than guns. You can’t describe every little detail in a film, because someone could get upset about it. The ratings are a guide for parents on what’s appropriate for their kids.