Re NPA theory and its propagation. Although most genetic studies of personality still conclude that personality traits are inherited, they still find only a 1-2% contribution from any one gene that they study. NPA theory postulates that a trait is coded for by a single gene or a small number of related genes (this deducted from the inheritance pattern noted for these NPA traits). Does this mean that the genes geneticists currently study are not the NPA genes? Not necessarily.
The reason they don't usually yield a causation percentage in the range of 50-75% (instead of 1-2%) relates to several things. One is the trait studied is not crisp biologically. That is, they may study, say, "novelty-seeking" but since novelty seeking is found in all NPA types and may be only superficially physiologically based, there won't be any significance found or minimal significance. Second reason is that the gene studied may be an NPA gene but it has different effects in some NPA types, an example being that COMT met does not cause modification of aggression in types without A trait. It may cause quietness and intellectual tendencies and higher IQ in types without A trait.
Another reason that current geneticists can't find 50-75% (instead of 1-2%) causation of a gene for a behavior issue is that, even if they wanted to study the classic NPA types, there is no current methodology to assign an NPA type to individuals to be studied.
So, it is clear why NPA theory's assertion that there are 3 traits of personality and a few modifications of those traits has not been laid out for all to understand.