Simple. When clicking an osu!direct link that leads to a post in a topic, when you click "View Topic", you only get linked to the first post. Now if someone wants to link you e.g. a post in a beatmap topic that deserves Kudosu but the Kudosu wasn't given you first have to go through every single post to see which one is meant. It would make things easier if there just was a "View Post" button which leads you to exactly the post the person linked you.
Did that make sense? Well you get the idea I hope.
Did that make sense? Well you get the idea I hope.