Whenever I write sentences of the form
I don't understand why X did Y.
I wonder why she did that.
I would like to know how you did it.
These sentences are actually not good examples of usages of these words "why" and "how" (and other interrogative words) where I find their usage not very sophisticated, but, right now, I can't come up with better examples. However, I am sure that sometimes I have the feeling that using "why" in similar situations to the sentences above doesn't sound very sophisticated. Or, sometimes, it looks like I am using "why" too many times, so I am being repetitive.
Are these usages somehow unsophisticated? Are these words avoided e.g. when writing a scientific paper or any other more technical document? My impression is that they are avoided. Is there a way to circumvent these usages? If yes, how would you do it?
Here, "why" and "how" seem to be used as "adverbs". Is this correct? By the way, would you call words such as "why", "how" and "what" "interrogative words", even if they are not really being used as interrogative words (as in the sentences above)?