Good posture also helps you breathe better, which can help you feel more energized and concentrate better. Your diaphragm doesn't work right when you sit hunched over, so your breath gets more shallow.
If you ever need to talk a lot for work or some other reason, good posture is essential so your voice sounds good and doesn't get tired too easily.
And it helps strengthen your core, which is good for balance and other things.
And the newer threads (from the last 1-2 years) often just aren't that helpful. Lots of people who don't know what they're talking about, or comment just to say they have the same problem.
I can usually get a helpful answer by trying a couple search engines or just fighting with Google, but it takes longer than it should sometimes.