Here's a example google image search for the terms "loaded touring bicycle." Most of the bicycles have drop bars.
But in the Netherlands, (with the equivalent term, trekking fiets or vakantiefiets) almost none have drop handlebars. Instead, all standard models like the Koga, have butterfly bars or straightbars with complicated bar ends.
Another google image search for "vakantiefiets"
I prefer drop handlebars because I like to rotate my wrists outward and I like the feel of grip tape.
Butterfly bars only offer two levels of the same wrist angle, unless you grip the far edge but that is usually too wide for comfort. My dislike of bar ends is somewhat petty- most are made of a hard plastic and I don't like the way it feels.
Ick, hard plastic.
But I wonder if my preference is also part cultural bias.
Or course, there are other differences too. Most dutch bicycles will come with integrated lighting systems, hydraulic brakes and o-locks... American bicycles do not.
I speculate that the difference in standard modelling is part of the difference in perception of cycling. Americans see it as mostly sport and in the Netherlands it's a much more varied activity.
Just a thought. Any others?