As others have commented - centralization. I have ONE place that I go to catch up on the internet. I don’t have to remember to check the 30+ ish blogs that I’m following.
It avoids any algorithms, so I only see what I have chosen to see.
Did you know that each and every YouTube channel has its own RSS feed? It’s far more reliable than YouTube’s own notifications.
It’s a far more pleasant reading experience than most websites.
There are several reasons.