I think it comes down to proportions -- not only block size, but also color and intricacy of design. I have seen many, many patterns that work well in smaller quilts. It may be that the patterns appealing most to you work best in king size quilts. In general, I think the smaller and more intricate block patterns work better in smaller quilts and large quilts benefit from larger blocks.
So much depends on the individual pattern. I do agree that an Irish Chain pattern in a king size quilt will look better with larger pieces than the same pattern in a crib quilt. About the largest block size I have used for that in a crib quilt was 2-1/2 inches finishes, I think. I can see why you would want to double that size for king size.