Possible additional reasons for the more restricted rating...
Images of people riding horses and motorcycles without... (*gasp*)... Protective Head Gear! Politically, socially and legally incorrect nowadays. Came to me after viewing Sonik’s motorbikin’ video and reading Suzy’s comment, “They need their heads banging together.” Wouldn’t surprise me if helmet laws were enacted governing the latter behavior or any subsequent activity which might result after such banging together of heads.
Images of a teenager smoking! No, no... can't have that, either, for the same reasons as above. Might give contemporary children a bad idea!