Thats what I thought! Cause even in school offices, they are supplied with AIO's. Its because they don't take up a lot of space on a desk, and leave a cleaner look. Believe it or not, if you had a full desktop with wires hanging off the back of it, customers are less inclined to think your a professional lol.
Studies have shown, that the look of your building, as well as the inside of it, can greatly determine, weather or not certain customers buy from you or not, or accept your services or not. If you can't be bothered to keep your workspace organized and clean, customers have less confidence in you.
I know the last time I was at a pawn shop, which was a heck of a long time ago now, but he had a completely disorganized desk. He had papers everywhere, stacked books everywhere, a full desktop computer, with wires going everywhere with no organization.
Then I took one look at him, and he also looked like he hadn't washed his close since 1975, it even looked like the moths got to it, and he smelled like he got the cherry BO from the last taxi cab he took. Suffice to say, when he asked me if I found anything that I was looking for, I said, nope, and left promptly lol.
So ya, computers have to be functional for the user yes, but keep that workspace tidy and clean people, the image you portray, is every bit as important as the features you have in the computer.