Users just don't care in general because there's no incentive to report posts, yet there is an incentive to boost post counts. See where I am going with this?
I do try to report posts every now and then when I see posts violating rules and everyone should be doing this imo to keep this place as clean from spam as possible.
Your report is marked as good if it leads to a moderator action. Everyone who reported the post gets it, regardless if they replied in the thread or not.
A post can only be reported once. I think OP meant that they were able to report the post, meaning no one prior to them reported the said post.