Why do I have to have my eyes dilated more than once a year

Pathology? The american academy of ophthalmology recommends yearly dilated exam after age 40. If you have some kind of retinal pathology then your eye doctor may need to dilate more often than this. Better ask them.
It depends. If you have any eye pathology, it is sometimes wise to have a dilated eye exam more than once a year. For example, people with diabetic retinopathy or macular degeneration may require more frequent complete eye exams to look for changes in the retina.
Diabetic damage. When the diabetes is uncontrolled or when there is diabetes damage in the retina.