According to the Chicago Manual of Style (5.21)
- People or things of higher status usually take the inflected genitive (in other words, adding an "'s" e.g. the chef's saucer)
The CMOS (ibid) gives an example of a nominative noun that is not of higher status, "Perils of Penelope." It is therefore written with the proposition "of" and not inflected by writing "Penilope's Perils." Why is "Penelope" not "higher status" just like "chef" is "higher status"?