Anybody can count who showed up. Leaders notice the chair that stayed empty.

Presence is easy to count and absence is not. Attending to who is missing requires holding the whole group in mind, including the people who make no noise by being gone, and that is a different kind of attention than running the room. It is also the one that catches things early, since people tend to disappear before they say anything.

Ask who has not been around lately and send them a message with no agenda attached. If someone has been missing twice, that is usually worth a direct question. Most people who drop out of things quietly are waiting to see whether anyone notices.