I don't care for age ratings
I doubt anyone else does, either. It just shows that the game has content that younger players (You, GreenBH) might find things that they shouldn't until a older age as it may scare them or something (Swearing, blood, gore, peels...)
Basically, it just means that "This is 18 because of the content contained in this game that younger audiences shouldn't find out about until the age limit"
Yeah...