Presumably, people see these mugs from the ISG gift shop after walking through the ISG museum (or less likely, before walking through the museum). I’m sure it is exceedingly rare to go to the gift shop without going to the museum on the same trip (perhaps to shop for a gift for a friend who is a fan of art). Therefore, these funny mugs are contextualized by the experience of viewing the high art of the museum. It’s this antithesis between the elegance of the art and the humor and irreverence of Isabella herself, who jokes that her “morphine or whiskey” habit is as bad as her “picture-habit, that’s so compelling.