As implied Oakley has the best polycarbonate based lenses out there in terms of clarity and being shatter proof. Oakley is still the king of sports lenses, until Trivex gains in popularity and overtakes polycarbonate that is. O Matter is super durable and comfortable as well. Glasses are getting more supple, whether it be less O Matter in each frame or a new blend of it, but they are light and wearable for long durables without it being too hard on the nose bridge.
Plus they have distinctive designs. Jaw Breaker, Racing Jacket, Radar and their various sporting frames stand out compared to everything else out there.
Because you can't buy 5 dollar sunglasses at the gas station that look like these!
Oakley has always made crazy cool frames that no one else would even attempt to make. Look at the X-Metals, who else makes something like that? No one!