You might think that, but it's a part of their culture, and it was a way for them to overcome violence. They used to be a very aggressive, violent race. Eschewing emotion was their way of rising above that. That is not to say they are incapable of emotion. They form close bonds and families, but they simply don't see the point in getting angry over things they cannot control, or being jealous over something they don't have.
I don't necessarily agree with it being the best route, but it is the route they chose and I see its merits.