Reasons to ask a question

I've been thinking a lot about communication (I know--fun, right?!) and especially about questions. This is because asking and responding to questions (not just answering them) is a large part of communication.

So, 12(+) reasons to ask a question:

1. To get an answer.
2. To force others to think about the question's topic.
3. To encourage someone to think about how they'd answer (even if they don't.)
4. To get attention. 
5. To get a response (that isn't a direct answer.)
6. To show (admit?) that you don't know (everything.)
7. To show a willingness to learn.
8. To show that asking questions is good/ok/acceptable/encouraged.
9. To show an example of questions that can be asked.
10. To show that you've thought about (or researched) the subject enough to be able to ask smart, informed, appropriate questions.
11. So others can hear the/their answer.
12. Never for no reason. 
13. Other?

I know the above is a generalization, and it won't apply to all scenarios but is a helpful summary of the things to consider.