You will often find scientists asking "Why" or "why does this happen?", etc. Why is the most common question for scientists. Other questions of interest would be How, when, what (or what if), etc. Scientists ask questions because:
- Natural curiosity: You may find that a number of scientists are simply curious to know about things and phenomena. It is this simple curiosity that drives them.
- Skepticism: Scientists are born skeptics (many of them are!!). They have to understand as much as possible about things and processes before they can accept something. Think where would we be, if we still believed that earth is the center of universe. It took a Copernicus or a Galileo to view this as a skeptic and figure out that that is not the case.
- Hypothesis formation: Scientists need more information to form hypothesis, a possible explanation for an observation. Only by asking questions, they can obtain as much information as possible to better understand the observation/s to come up with a reasonable hypothesis.
- To learn: Scientists do not know everything and most of the times, an observation may require more than one expertise to come up with an answer. Scientists ask questions to know more about other fields, so that they can incorporate that knowledge in their work. For example, an biologist may also need to know statistics to describe his/her data and will therefore ask questions from a statistician.
Hope this helps.