Questions breed greater thought. A child that doesn't ask questions may sometimes show apathy. It may show that he's not interested or concerned. It may mean that he couldn't care less. If someone is concerned and really wants to know then he will ask questions.
Questions stimulate the mind toward greater knowledge.
In Torah, one can never know everything. The Torah represents G-d's wisdom which is infinite. One can never learn enough. Questions enhance a person's knowledge. It keeps him growing.