Wearing sunglasses should not be reserved for sunny summer days only. It’s important to wear them even on cloudy days cause there is UV light on cloudy days and during other seasons of the year. It's better to protect our eyes all year round.
My doctor friend advised me to do so for UV protection. However, I don’t like to wear sunglasses if the sunlight is not so strong cause I think they will darken my vision.
How to say, for the health of your eyes, it is necessary. But I don’t believe people would follow it. It could be a little weird if all of us wear a pair of sunglasses on a cloudy day.