Depending on how much influence with companions you have, the influence itself can do various things for you. For my character, I've had it happen a couple of times what when I failed a conversation check ( bluff, taunt, intimidate ), Gann/Safiya/Okku would do it for me.
The other thing that can be very helpful are the feats/bonus stats you and your companions gain after you reached a certain level of influence with them. Check
here and select the MotB companions to see what they do exactly.