Pleasant to deal with

We are monkeys, advanced monkeys with a mix of new features, but a bagage of primitive ones.

We still use "impression" to grant more credibility to some other individuals rather than others', regardless the value of their arguments themselves. Which is obviously a sign of stupidity, but hard to overcome.

Hence, being pleasant to deal with is a higher advantage that overshadows, unfairly, technical skills and understanding. It's somehow understandable from the efficient point of view. If the cost caused by friction when dealing with a harsher person, or a person harder to make agreements with, is higher than the value of their specialized skills, it's compensating such advantage and can be replaced with longer learning curves from another monkey that could anyways learn sooner or later the same skills but is easier to deal with and make agreements and find understanding gaps. 

Conmen know it and try to overcompensate their lack of skills, and their lack of interest in developing them, by being too nice. But even most of them face challenges because that's not something we can fake. How nice is to deal with us depends on what we truly think and feel, what we believe. Any small gesture could betray us if we're faking it and the result would be worse than us simply being honestly not enjoyable to deal with. We don't excuse fake friendshipness, and especially if it doesn't come with eventually good results.