I don’t think that Starbucks coffee is all that unique. When consumed without sweetener, it’s a bit generic and has little personality. I think that explains all of the flavor options.
@chet it's to guarantee consistency, the over roast/burn their coffee. Thus, no matter which Starbucks you go you'll get the same flavors
@Gabz it’s the right blank canvas on which to build their drinks. It also means that the drink is about the flavoring. The fact that it has coffee in it is ancillary.