When I was growing up in Kansas I always thought to myself the sun doesn't bother me why would you wear sunglasses? I know you most likely know but the answer is simple UV protection. Moving to Texas the UV index is a lot higher than in Kansas so the importance of UV protection increases dramatically. Another reason not a lot of people think of is that according to the National Highway Traffic Safety Administration sun glare is the second environmental-related reason drivers get into crashes! (the 1st is slick roads) and polarized sunglasses are recommended with this because long story short it removes reflection/glare from almost everything see two examples below. It does this by removing all horizontal light bounced off of a surface.
There are over 3,000 fatal car accidents in Texas alone each year and it wouldn't be surprising if some of these could be caused by sun glare, which means it may save your life or someone else's life by just sunglasses and fighting glare!
Now let's go over some of the cosmetic reasons UV (sunglasses) protection is essential. You normally hear for using sunblock/sunglasses is it prevents wrinkles on skin which is true and big part. Just reminder that 5 to 10% of all skin cancers happens around the eyelids! UV protection also helps prevent things like pinguecula see image below.
This can be very annoying to look at and is caused by a combination of UV damage and dry eye normally but can also develop into a pterygium see below.
If it gets into the pupil it can decrease vision and/or cause a ton of astigmatism too. Surgery can be done to remove it but using sunglasses and treating the dry eye can completely stop this from forming in the 1st place. Some of the most common diseases that have been linked to UV damage in the eye are cataracts, Choroidal Melanoma (from Freckles inside your eye), and Macular Degeneration. 15 million people in the united states have Macular Degeneration alone. So I think the simple question are you wearing sunglasses?