It seems to me that one of the most foundational parts of the way someone sounds while singing comes from the intentions and circumstances they had when they were practicing - when they were learning how to sing. Classical singers pretty much all received professional training, usually from a young age. One cannot really just decide to become a classical singer without the means. Other genres like blues or folk are quite the opposite. Singers are encouraged to figure their voice out for themselves, by themselves. I think that if all blues singers were trained, like classical singers, and all developed the same techniques, then the integrity of blues would have been undermined.
That being said, it seems that when someone says 'a blues singer', an archetype does come to mind. I believe my point remains, however, because that archetype is an extraordinary example of the individualized and highly expressive methods of practicing I was discussing earlier. These individualized methods remain even if the singer has an archetype to consider sounding like - it being important that they do not have to sound like the archetype.
This I feel to be just one of the windows through which to discuss the 'angles' of different kinds of music. Blues seeks to unleash the innermost feelings of the musicians. Classical music seeks to provide a place to play with different technical musical 'tools' or techniques. And music that pushes these boundaries redefines what can be expected from any genre. There are infinite possibilities, all of which worth trying.