Could also be people coming from All, so not members of your community

Yup, and on the flipside, I suspect this is also a 'fortunate zone of discovery' that we can enjoy these days across Lemmy.

For example, on Reddit, there's barely a chance your sub will be randomly seen on ALL unless it's fairly big and well-established. Which is why I tend to urge people to make the community they want to succeed right now and here on Lemmy. Don't complain; do it!

Because in future, that opportunity may no longer be there to catch so many ALL viewers, assuming I'm right in that.