Why questions are very good and should be encouraged! But also, it is worth improving the questions, in addition to just answering them. So if a child asks "why is the bus going?", you can ask for a clarification "Do you mean what makes it move? Or do you mean where is it going?"; this models clearer language and better communication skills, it helps the child get an answer to the specific question that they intended, and it prevents why-questions from becoming the default I'm-bored-so-I-will-say-why-until-people-get-sick-of-talking-to-me routine.
Sorry, I know that was slightly off-topic.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.