Lately I read all these blogs extolling the virtues of single dosing. Why? I will not attempt tp defend full hopper dosing in this blog since it needs no defending. Go to your favorite coffee shop and point to a bag of beans they roast and sell that is not - repeat is not - the coffee being used for espresso. Wait patiently for the barista to change out the coffee in the grinder and exchange the beans in the hopper for your selection. Be very patient - this might take several days in a slower cafe.
Point is they do not single dose. They load the hopper, dial in the blend, and pull shot after shot till the beans are gone - as in there are no more beans like it in the building. See folks, hoppers can be refilled with the same beans! They usually are in fact. Why mess with what is pulling fine and tastes right? This is a fact of life in most espresso cafe's I see. Most cafes, unlike the typical coffee geek's kitchen, only have one espresso grinder! Can you believe that? Three groups but only one grinder - what is up with that?
Simply put, changing espresso for every shot is something only a home enthusiast would attempt or even appreciate. Ask the cafe owner why he doesn't offer 4 blends - he will say if they don't like my coffee why are they here in the first place? They expect a compact of trust that they can use their beans, grinder, and machine to create an enjoyable shot - if not they will gladly bury it in milk, sugar, or ice if necessary to keep your money. Most times the shot will be right and tight.
Most home baristas do not control the feel an flow of the machine like someone pulling 30 shots in two hours vs. pulling 30 shots over a week so we tend to measure twice and cut once while arguing more about the ruler than the quality of the cut - or cup.