Would be nice if an author of a question can see how many people are writing their answers.
I don't see how that could be much help. Would it have really helped you to know I was writing this answer? There are already plenty of mechanisms to allow you to see if someone has posted an answer to your question: the emails sent, the summary you get when you press the envelope, the notification bar at the top.
It's easier to do something else instead of just seeing 3 people are replying to your question. What if they all cancel? What if it takes them a lot of time to answer? Will you just anxiously wait for them to finish? I'd rather answer some questions or simply browse around. If someone replies, I'll see it almost as soon as they've finished, which is OK for me.