rattie, what you're saying is sometimes true about female contestants.
But when it comes to male contestants, if they Initially sounded bland to you, they tend not to improve on that impression.
It's only when you hear a male singer for the first time, and can immediately spot that he has a uniqe and quirky voice, that you recognize that he may well be exceptional.
With male singers, it's not so much about "good voice" (as with female singers). It's much more about quirkiness.
Consider the following singers:
Joe Cocker
Rod Stewart
Bob Dylan
James Blunt
Their unique voice is more interesting to listen to, than a classic "good" (but boring) voice.
That is why I'd expect the x-factor to opt to promote male singers like Mali (for example), instead of Scott, Eoghan and Daniel. To try the unsafe-quirky ones.