How else are you supposed to gawp at scantily clad ladies surreptitiously? Generally they're not so much sunglasses as perving goggles.
While I sort of agree (I'm not into labels) you need to remember how some labels became designer. Oakley for instance made sunglasses and other eyewear with no distortion first and foremost so that people could do various sports more safely. The cheaper brands put no effort into this and I've had several cheap pairs which have had odd lensing effects which make quick reactions for things like cycling impossible, Only once they were associated with sport did others start to buy into the brand to look "cool". Same goes for Musto, Henry Lloyd and other sailing brands - they made good kit and worked their way up to being a label. They still make good kit, and probably still considerably better than the cheap stuff but unfortunately the premium price puts many off. It's worth some investigation as to why something is popular beyond just assuming it's a label