It’s simple: engagement.
I have a Twitter account for engagement. If I post on this blog, it pushes automatically to Twitter. It allows those people in my community who want to get updates via that platform and either comment or like my content to do so.
Otherwise, I would not have Twitter. I’d delete my account like I did way back when to Facebook (Yes, I know, I have a new account there that I do not use, but I digress.).