You need to account for the risk of blackmail, persecution, and embarrassment (e.g., evidence of infidelity, refugee status, medical condition). Most of the time, citizens have the right to keep secrets or lie.
Citizens - yes. Politicians outside of the job, using whatever comms they wish - also yes. Politicians on the job - no. All their job communications can be public, and humanity and citizens of the country would be actually much safer than now. Outside of the military/intel ones, of course.
I imagine that any dump of government communications will contain sensitive information about citizens or government employees who didn't directly engage in the chats. Soldiers, contractors, patients in a database. Especially if Congressional Representatives have their chats leaked. One of their roles is helping constituents work through red tape. Mine sends a weekly email tooting his own horn, including how many people he helped with social security or getting VA benefits.
I'm not saying these chats shouldn't be released. But I'd hope the names and other identifying info of people who weren't uninvolved would be redacted, just keeping the context to show what kind of information was being carelessly shared. Of course, given the admin's shamelessness, they'd claim anything with redacted info was faked. It might be better to leave it verifiable.