He only started to do it because people started to call it out when he was absolutely wrong about some cards and how confident he was about his rating.
At this point its just more content now, just another video for his channel.
I know, dude, but you're totally missing the point. How many streamers out there do the same? Do you really think he has some kind of obligation to do that stuff, stuff that can backfire him sometimes considering how weird are some members of this community?
It's not truly an admirable feat. He's a streamer; his brand thrives on content and perceived transparency.
You know nothing about Trump then. He is not just a streamer, he is the most iconic Hearthstone streamer (even when he is not that popular right now). He was considered by most players to be the smartest Hearthstone streamer when this game was young and yet he is doing stuff like this right now. So yes, it's truly an admirable feat.
If you watch the video he mentions that he has an 87% accuracy rate on his ratings within the first minute, so at the very least he's kind of humble bragging. Additionally, as a YouTube creator you want to make videos that attract views and stuff like "my worst ratings" etc. is exactly the type of content that gets people to click and make you money. It also gives him a chance to justify his own logic at the time instead of having someone else make a video about how wrong he was that paints him in a negative light, like this guy: