Most Full Black Bloods have some sort of powers. Along with most being very intelligent (Enough to develop technologies hundreds of years before Humans) one of the types of powers you can have is super intelligence. However, since a lot of famous families are incestual, they sort of breed-out the intelligence gene, to the point where the children become as intelligent as the average human (not stupid but not nearly as intelligent)
This is why the few allowed technologies are so old and simple (Radios, small TVs, light switches, oil lamps, etc.) because either A) Citizens don't want new technology because it will disturb their carefree lifestyle; B) Leaders outlaw it in fear the citizens will out-smart them (Which is why incest and polygamy is often enforced); or C) They only know how to create those things because the intelligence gene has been bred-out of them.
As for emotions, I probably should have been more clear.
Black Bloods tend to have very strong emotions. Many black bloods cannot express certain emotions because of how strongly their brains express a few other emotions.
Example: A Black Blood might not experience Sadness because of how strongly they express their happiness and anger (Though it should be noted that many Black Blood families tend to have children with more sad people, so the happiness gene is often absent in many young kids; It's mainly because it's either a law, or frowned upon because happiness doesn't match the planet's somber aura)
A more common forgotten emotion/feeling is guilt or remorse. Many leaders and future guards are born to an unhappy couple so the chance of happiness or remorse is often low. More Black Bloods do this now, as it has become something of a trend.
Some places have outlawed feeling or expressing certain emotions. Many of the prison island don't allow happiness. Many places dislike remorse or guilt.
While rare, it is not impossible for a black blood to be born with all his/her emotions. It is just either very rare, or illegal as many who are known to show their emotions in many ways are imprisoned for being "different" than the picture perfect society.
They realize they are different and missing emotions, and often long to feel those emotions. I said they were often sad and angry because those are the most common emotions to feel.