Edit: Wow some weird haters on HN today. I was honestly curious as an active signal user that was no longer able to use it to message people in North America and had never seen anyone using it in East Asia. Apparently this makes some other signal users very angry.
The SMS issue was mainly a problem in the US where people used it for SMS and therefore never mattered since that communication was never secure. Those people probably never even cared for security since they, as you said even went out there and actually uninstalled an app. Something people seem to rarely do.
I use it for friends, family and colleagues. People now started asking me for it (or safe alternatives to Facebook Messenger) since Facebook started asking people to pay for non-targeted ads recently. They actually got people to think about the data they share with an outdated social network.