After some thinking I got an idea: To answer "Why?" is the key for scientists. When you write a paper or do a research you have to be aware of this. Furthermore, I feel this (intellectual curiosity - if I translate correctly) is probably the reason of my life - or the answer to the question "Why are you going to become a researcher?"
It is possible "How?" plays the similar role in the case of engineers or scientists in some fields. But "What" "When" "Who" are something related to news. Just reporting them does not enough for e.g. a scientific paper. I has been wondering what makes technical reports different from the research article. This is probably the answer. In a research article you have to answer "Why?" cuz ultimately it is what the readers of your paper expect.
I am going to occasionally write my thoughts in English like this as writing exercises.