Eric Church didn't start wearing sunglasses onstage to make a fashion statement. Quote, "I wear contacts and my eyes don't do real well with lubrication, but we would play all these bars and clubs.
"The lights would bake my contacts and they'd fall off. So I ended up being blind on stage. Someone suggested glasses and it worked, it ended up being a thing."
It's to the point now that he doesn't feel right if he's onstage WITHOUT his shades. But he doesn't wear them 24-7, just when he's performing.