One possibility might be leaders who have found there are members who aren't receiving LCR emails, and are trying to ensure communication reaches everyone via individual emails, but also want to know who has chosen not to receive church emails. Or group communication via text or WhatsApp, which naturally occurs without using the Church's system.
I might have a member in my personal contact list, and assume that I can add him into whatever Church communication I'm organizing (outside of LCR send-a-message), without knowing he has limited his Church communication preferences in his member account.
To answer the O.P., I'd suggest that in the original outreach for whatever effort you're doing outside of LCR, it would be good to include a note that anyone desiring not to be included, simply contact the "organizer" and request exclusion. As an example, our records were recently moved to a new ward, and my wife was automatically included in a group text for the sisters. While there was nothing wrong with the desire to have her feel included, there were a "gazillion" (her words!) daily texts back-and-forth which showed how much the others were enjoying it, but she finally requested to be removed. The "organizer" felt really bad that she hadn't reached out to let my wife know about the text group, and never asked if she wanted to participate. Just a personal example of where a member wants Church LCR emails, but not necessarily all communications, and it isn't even related to any "data privacy" concerns.