Why some people afraid to ask questions to clear their doubts?

There are lots of ways for us to learn new things: we can go to school or college for it; we can research it online; we can observe somebody performing it; we can listen to somebody speak about it; we can go to a training workshop in real life or online and also we can ask questions. Usually, we ask questions about stuffs we don’t know or for the reason that we are searching for data or explanation. Then why some People afraid to ask questions to clear their doubts?