But you may have missed the memo because you're in the wrong time zone, and with Slack, your possibly-relevant input is ignored because you can't participate in real time.
This is my beef with chat. As the OP says, it biases all conversation to those in the same time zone. Fine for some things (like baked goods arriving in some far-off kitchen), but not for others (like a design decision that should have input from stakeholders around the globe).
But it's often used for the reverse.