Because I find video recommendations useful, because I want to upvote good content on the internet just like I do here on HN and because I actually have a nice timeline with curated content. The points of the article are rather weak to me, specially considering you are supposed to have good security for your accounts so even if you decide to actively log out yourself the next time you'd like to interact with any of these networks you will at least have to go through a manual login, 2FA using your phone and an authenticator app etc, it's a bummer so convenience wins there. If this is a problem then, I believe convincing people to never save login passwords in their browsers is more compelling than suggesting to log out. That said, if I could log in with Face ID in like 2 seconds everywhere I'd probably stay logged out until I wanted to interact in SOME networks.