If doctors were to stop prescribing sunglasses, would poor vision and cataracts increase?

Unlikely: Sunglasses are an individual choice and rarely prescribed by ophthalmologists. Patients are given a prescription so that if corrective sunglasses are desired, then the patient can get them but it is their choice. The overwhelming majority of sunglasses are obtained over the counter with prescription. Failure to use sunglasses is sometimes uncomfortable but will not cause pathology.

Yes: Poor vision, because you would not see as well as you do with your best corrected vision. A long term decrease in vision would only affect children less than 10 who didn't receive glasses while their visual systems were developing. This could lead to poor vusual dfevelopment (amblyopia) and a lifetime of poor vision. Increased uv exposure increases the risk for premature cataract development.