I mean, what if you submit 3 stories and only the first gets published on that day. But someone else submits your third story as their one for the day and it becomes the most popular item on HN that day. Suddenly you're annoyed because you think you should have gotten those points.
Maybe you could have a queue but if someone else submits a story you got to first and was queued than you both get the karma points. There's nothing that says only one person can have the points for one story added to their total.