I assume my private messages are always public record, so I don’t get this mindset. My first thought when messaging someone is, “What if they screenshot or leak

I assume my private messages are always public record, so I don’t get this mindset. My first thought when messaging someone is, “What if they screenshot or leak this conversation?” or “What if their message history is subpoenaed?” It never makes sense to assume confidentiality with other coworkers.