If I understand correctly, an individuals' expectation of privacy in a public place or gathering is not the same as it is at home. A person may refuse to permit a recording within their private home, of course. They may decline an interview with the press anywhere if they so desire. But they cannot prevent a recording in a public place.
Those places or churches that obtain releases from adults are taking a "belt and suspenders" approach, I believe. Once it is generally known, or obvious, that cameras are in use, a person gives assent to being part of the recording by their presence.
This is hopefully never the case in a church, but if the recording were used to demean or defame an individual, then they would likely have grounds for legal challenge. But merely being captured in a video as being present? I don't think so.
Children now, are another matter. I would tread more carefully in children's ministry spaces. I would have releases or refusals from every parent, and respect those refusals. When we have children involved in video productions, we get separate releases from the parents for that production. That's just me being obsessive.