In the 3 years or so since I installed Signal, I haven't had a single conversation on it. Only a handful of people from my Contact book are showing as Signal users, and none of them people I speak to regularly.
I live in anticipation of someone deciding to message me on there, but I'm not exactly optimistic at this point.
I met one person a few months ago who also used signal primarily. It did feel weird adding someone normally. Usually when I add someone it's their first time with signal
It's not about converting people close to you. In some situations, you're asking them to install an app just to talk to you, while everyone else they talk to is on WhatsApp. I personally have to use WhatsApp for work and for personal, otherwise I'd literally not get those messages. There's no option when, if you stop a random person on the street, regardless of what OS their phone is running, and ask to look at their phone, it's going to have WhatsApp installed. It's like your phone having email; who the fuck doesn't have email? It's the same with Whatsapp, it's just assumed you have it.