Because who in good mind would recruit most of these companions in the way they are presented? I think only SH and Lae would make sense since you meet under certain circumstances that can create an easier bond to at least work together.
Shadowheart tried to murder my character, so nope. Though she is at least honest enough to admit how far she is willing to go for Shar.
Wyll and Gale are the only ones that didn't show any killing urges towards the main character so far.
