I've been heavily involved in an active-active session service that handles 100kqps+. It's not that hard to achieve with Redis.

If you model your sessions as an acyclical state machine, you can quickly consolidate a single view of all sessions globally.

Beyond this, it's valuable to be able to scope sessions, invalidate subsets of sessions, create delegate sessions, provide an audit trail for internal support staff using session impersonation, etc.

JWTs can't give you a lot of the rich security behaviors that real sessions can, such as asking a user to use 2FA for editing sensitive data if they haven't provided that information in the last 15 minutes. Or estimate user idle time.