It forces the blogger to get to the point. Even most blog posts shared on HN could have been a tweet or two.
Instead of having "upvotes" or "reactions", this function would be the same as replying a single char or two. If multiple people post the same thing (like "" ":)" "L"), it gets collated and boosted as a single message.
If you want to flex, you can drop $10,000 to post a 10kiB picture of your dog. Or spend $1000 to write an overly long post. But I imagine long posts would be seen as bougie.