Yes. Privacy and password security.
Privacy: so that people on the same network can't see what you're doing. This especially goes for Wi-Fi networks, but also to keep frelling Comcast from inspecting everything.
Password Security: So that your passwords can't be intercepted mid-transmission. Everyone here is of course using a unique password for TW (right?), but this keeps your TW account and credentials from being used as a springboard for getting into your other accounts.
Certificates are free these days (Let's Encrypt), so the cost of doing so is trivial compared to the site's operational costs.