Sometimes when people post their questions here, they are incomprehensible but still receive an answer. The person who answers intelligently may correct the question in it's spelling, grammar and punctuation before providing their answer. This way, they make what is being asked clear for readers while also providing a well thought out answer .

Musing encourages rewarding users for quality posts. If someone were to gain from a low effort or spammy question because of someone else's hard work I don't think that would be fair. 

You do bring up a good suggestion  in your question description where it could be an optional checkbox and both parties gain. On the other hand it could also promote rewards for low quality question posts.