Ask HN: Does Signal fail to be a decent WhatsApp alternative

As like many over here, I started looking out for alternatives to WhatsApp to move my personal communications to. A good HN citizen suggested Signal by WhisperSystems. Seems very good on paper, until I downloaded their app and tried to use it. Signal (their iOS app) needs access to Contacts to work. Why?! (1) Why should I trust them with my contacts that I'm NOT reaching through their App, (2) Smells the same like WhatsApp where it is only a matter of time, where they sell out and start selling my contacts for "correlation" value at least. Am I wrong here? Anybody know more?