The sad thing is that even if you don't give a shit about other people, it would still be beneficial to make sure everyone is taken care of.
Imagine if we didn't have to worry about people stealing our bikes or breaking into our basement because everyone had enough money to not have to steal stuff.
Or if we didn't have to worry about our kids getting a good enough job because even if they follow their passion their jobs would still pay enough to have a good life.
I think Signal is trying too hard to be secure, and they are missing a lot of convenience features.
For example, you can't migrate from Android to iOS or vice versa. You'll lose all your messages and groups.
Or it's really hard to export all the photos someone sent you. I get that my iCloud library isn't as secure, but I really want to make sure I don't lose those photos if I lose my device. The photos aren't that sensitive.
The security notifications are also well-meaning, but hard to make sense of. You sometimes get notifications for changed security numbers, when people change their phone, sometimes folks show up twice in groups, etc. It's all a bit hard to understand and difficult to use.
And finally, it seems that messages are sometimes delivered a bit unreliably or with a long delay.