Is there any benefit (other than it's easier) to have all the different categories on the same site? To me, it seems that "a site that lets you compare stuff"

Is there any benefit (other than it's easier) to have all the different categories on the same site? To me, it seems that "a site that lets you compare stuff" is less appealing than "a site that lets you compare girls", "a site that lets you compare cars", "a site that lets you compare pets" tied together in a loose network and with similar branding. Also, I should be able to vote by just clicking on the image I like more :p