Because of family phonos shared between me an my siblings, and between me and my wife.

All our communication is over signal, so it is a nice record to have.

I look up old iMessages, emails, group chat comments, and so forth constantly, often finding valuable gems of wit, reference-material, recommendations, or media that I dimly remember from years or even decades ago.

Signal and other messaging apps offer a 'search' bar across all sessions & history, so I doubt I'm the only one.

It's hard for me to imagine being so present-focused such a history wouldn't be personally useful.

Or, so worried about "someone [using] it against [me] in court" that I'd need more than the occasional auto-expiration, and specifically my messenger "protecting" me with intermittently-enforced loss-of-histories (on just theft/loss/hard-failure of primary device).

I have messages from a deceased friend. I find it comforting to read them from time to time.