* sub-par user experience: WhatsApp is just nicer and smoother, and people tend to like that
* very few people understand that Signal DOES NOT get your full contact list, while Facebook (through WhatsApp) does
Especially the second point is very relevant with the current situation — you do not necessarily want to expose your entire social graph to Facebook. But so few people understand this, and even fewer grasp that Signal can still work without doing the same thing.
Why does it "really hurt" Signal that are sub-group of the population is ignorant of its features? I doubt that's going to stop people from downloading a privacy app, most people don't care about privacy anyway, and if they do, they will DL signal.