If you’re not on WhatsApp, no updates or news from your kids school, your sports team, your family, your car dealership etc. for you.
But since January the trust in Meta has not only plummeted but it's become a mainstream enough talking point that I now receive invites to join Signal groups from--for want of a better term--normal people. Two of the local parenting groups I'm on are on Signal and no one ever mentions it or questions it, it's just "here's the group link" and the expectation that everyone has it installed.
I switched phones and lost all my history. Now I’m fairly careful with these things, and make backups, but even I wasn’t able to get it back. Couldn’t recommend it to anyone since.
There’s a line between being secure and being useful, and they’re slightly unbalanced in Signal.