I know they don't have small on the menu and I'm quite sure they don't have "coffee" either, but I always get what I wanted.

Starbucks is IMO beaten only by Subway in the field of making it unnecessarily difficult to order the one thing the company is nominally in business to sell. If I want to micromanage my sandwich on a tomato-by-tomato and dressing-by-dressing basis, I'll make my own sandwich. If I'm buying a sandwich in a shop, I expect the shop to have done all the difficult design work already, and to present me -- they are, after all, meant to be the sandwich experts -- with carefully-optimised results that are good in ways I wouldn't necessarily have thought of myself.

Peter