It seems to me the reason hipsters all look the same is because we tend to lump things together that resemble each other 'close enough'. If a person has thick glasses but is wearing a backward cap, are they a 'bro' or a hipster? It will probably depend on whether there are other hipsters around--if there are, you'll define that person as hipster. If that person is in a sports bar with bros, then you might say that person is a bro.