" it doesn't seem like it would be very hard for shimano to make an appropriate hub, if they wanted to."

It wouldn't, but how big of a market would there be for it? Quite small, which would make it expensive. Since you have to spend the extra money, it makes more sense to invest that money in a stronger wheel and keep your gears.
Although many people are totally content with "wide range" gearing, others that ride the flat lands like a lot of closely spaced higher gears.
I have bad knees, and thus find my cadence to work best in a rather limited range. I love being able to shift to a 1 tooth different cog if the headwind changes slightly, and repeat if it changes a bit more. Currently, my largest cog is a 23T. (12-13-14-15-16-17- 19- 23)