Except that they make it a pain in the ass to save the stuff you want, because there isn't an easy 'export conversation' function. You can archive conversations so that old ones don't clutter up your chat list, but the only thing you can do with an archived conversation is...un-archive it. It has literally zero utility.

Your only way of saving things is to either manually save every picture and video, or manually highlight and copy the text in your conversations. The latter defeats any security arguments (other than of inconvenience) but also throws away useful information like timestamps of messages.

My Signal database takes up many GB on my phone, and it's constantly complaining about running out of space. Much of this is the years-long record of conversations with my wife. I'd like to back these up, but I can't. Are you gonna tell me that I shouldn't be using a secure messaging app to communicate with my own family members?