I have no idea what you are talking about. The world's largest coffee chain (Starbucks) uses a single 1 oz/7 g espresso shot in their short (8oz) And tall (12oz) drink sizes. To get two shots you have to upgrade to "grande" (16oz), or specifically ask for (and pay for) an extra shot. Most coffee shops do the same for their smaller drinks.
Starbucks does use singles in some Tall drinks (your point stands - Latte & Cappuccino), but not all (Americano & Flat Whites have 2 shots in a tall).
Meta: I've never seen anyone order a short, the only thing I've ever seen in those cups are espresso pulls or water (but it turns out a Short Flat White still has two shots - worth a look)
Starbucks makes coffee flavoured desert drinks. We are talking about specialty coffee shops. I've also never seen starbucks use a single shot basket to pour a single shot. They always just split, this is broadly the standard. Nobody outside of Italy is making single shots with a single shot basket.