An upvote on a question fetches +5. Whereas an upvote on an answer fetches +10. Why is this so? Isn't asking the right question important to get the right answer?
The site is about getting answers to questions, so it makes sense to award answers more.
It's much easier to ask a question about something you don't know the answer to than it is to have the answer to a question.
Finally - answering a question is providing direct help to someone, whereas asking for help is requesting someone give up their time for you.
The fact a question remains open and appropriate enough to get answers is basically its own reward. If someone chooses to take time to provide a solution then that is something more worthy of a reward than just being able to articulate a problem. Giving a reward for asking a question is really just a way of encouraging content to the site. But giving a reward for answers is a way of encouraging quality, useful content to the site.