As a roaster who does not run a cafe, but sells coffee to many artisan coffee shops, I have my own perspective on this issue.
I think Abe makes some assumptions here...
First of all, Abe has made an (apparently unchallenged) assertion that milk drinks are "better" than straight shots at these cafes. I don't find this to be true, myself. Lots of these artisan shops produce espresso to a very high standard, and I will say that I have really thoroughly enjoyed lots of the straight espresso I have had at these shops. I'm still trying to figure out what standard you are using, Abe. I understand that you like the espresso in your kitchen better than you have had in these shops. But isn't it possible that those shop owners and baristi would enjoy the coffee from their shops better than your kitchen espressos? Which is of higher quality, again? But maybe I misunderstand you, Abe, when you talk of the "artisan" shops, you are talking about the new movement of very quality-focused shops that have blossomed within the past few years, right? Not the starbucks-imitating big-milk drink places, right? I assume that is your reason for using "artisan".
It is only somewhat true that certain coffees do better (according to taste) than others in milk drinks. Our La Forza blend (relatively intense) is the best suited for milk drinks, in our opinion. Aficionado (delicate and layered) is a straight shot coffee, to me. Toscano (sweeet) is a straight shot coffee as well, but has better performance in milk than Aficiconado. However, there are baristas that prefer Forza straight, Toscano in milk, and so on. An awful lot depends on dosage, temperature, concentration, etc....
Most of the owners and baristi in these "artisan" shops are straight espresso drinkers. I know I am, and I was an integral part of the blend designs (along with baristas). These people drink their own shots all the time. Do you think they drink a shot, shudder, and say to themselves "that sucked, but I choked it down because it would've tasted great in a cappuccino"? I feel that these shop owners and baristi are serving espressos they feel are a great representation of espresso flavor. In my experience, baristas get really excited when they get a straight shot drinker (they are so rare, after all) and they try extra-hard to please them. I think your assumption that these shop owners are intentionally sacrificing straight-shot quality in order to make good milk drinks is off the mark.
Addressing your points specifically:
1) Shots are way too concentrated. In a cappuccino, such concentrated shot is transformed in milk and yields a wonderful cup. But using the same parameters to brew a straight shot is doomed to failure in many instances.
Many baristi have embraced overdosing/underextracting for a long time now, and not because it makes the cappuccinos taste better. I understand that you might not like super-thick shots yourself, but many do. This is changing, now people are going back and exploring what less-concentrated drinks can be.
2) Coffee is just not suitable for a straight shot. On a good day it will reach the high mark of a mediocre drink. On most other days, it is flat-out bitter, but man, it looks so good in the cup.
Could be, although as I said I think most owners of artisan shops try really hard on their espressos and drink them themselves. Do you really think these baristi intentionally serve flat-out-bitter shots, rationalizing that at least it looks good?
3) Coffee is suitable but coffee shops are not setup for efficiently changing grind/dosage parameters between an espresso & a milk drink.
This is true for sure.
4) Just lazy baristas
I gotta defend the baristas here; I have rarely met the barista at an artisan-third wave shop who was not enthusiastic, hardworking, and passionate about espresso.
Peter G