This is why it was so good that Signal supported SMS. It was much easier to get people to switch when they didn’t have to think back who was on Signal and who was not before starting a conversation. Now people just default to text because they know everyone has that, and they don’t have to waste time opening Signal, seeing yup, not on there before opening their SMS app, if they even bother.
One important aspect is that two peers without port forwarding will never be able to connect to each other. This is important for torrents with low amount of peers. Unless a connectable peer comes in to essentially relay data by grabbing the content from the other person and then seeding to you, you won’t be able to download. For popular torrents with plenty of connectable peers to go around this is less of an problem, it will only cause some performance issues.
Fun fact: on Android after not using an app for more than three months (the exact time can vary by manufacturer) the OS will remove permissions including notifications (suppressing the app’s ability to run in the background) to save battery. So the app will literally stop working.
For a seldom used app like Signal that’s hurt from a lack network effect, this triggers a death spiral outside of the privacy enthusiast community. When it had SMS support this guaranteed some usage, but now that’s gone.