Sometimes they do get exposed though...
For example people gave Paul Williams credit for outboxing Margarito, and he was looked as a huge boxer... But he got exposed as nothing but a glorified brawler (nothing wrong with that, but its a limitation) against Martinez
Andre Berto got exposed as a front runner against Collazo, and the role of the so called boxer that he played in the media got exposed when he had no answer for Ortiz
Khan got exposed as a fighter with all talent, no brains in his fights with Peterson and Garcia... Take away his speed and athleticism he'd be Vivian Harris