The Voice Part II - As the Show is Progressing are there any "voices" left...?

The Voice. What is the purpose of the show? Are the judges looking for the next Susan Boyle or Paul Potts for that matter? And if they are, it is not such a bad thing, provided that the contestants remain to keep the quality of the voices that they originally came with. Due to my trade, watching every singing contest/competition under the sun, it seems to be that they have the same pattern where the judges pick, in most contests, the top of the top, cream of the crop singers to start with and then, for some very strange and mysterious reason, the contestants begin to deteriorate by each consecutive episode. The reason is unknown...?

My guess would be that either the contestants are trying too hard to win (nevertheless, "to help their families") and/or the so called coaches (i.e. actual singers and producers and not exactly coaches), are not really helping them to achieve the "absolute heights" with their voices. This remains to be a riddle, but since these auditions were blind in this particular case, and weren't based on looks, then what's left, you may ask, if not the absolute awesome voices. 

Just like Susan Boyle, whose career seems to be is not on the rise now as it used to be before a "hiccup" on The View, my guess would be that she's most likely experiencing a lot of difficulties to pick up the pieces (do to her voice problems), as beyond the voice, nothing much would be going on for her. She's not exactly projecting any sexual appeal or able to dance and prance on stage like Britney Spears. Similarly, my question is, what will be left of the, let's say, Top Three or the Winner, outside of the "LIVE" video portrayed on stage (which is very much so in fashion these days)? 

Frankly, I don't profess to know...