argument to install Signal is pretty easy - I just ask Android users if they use Facebook Messenger to manage SMS. if answer is negative I propose why not use different nice SMS client called Signal which can also do encrypted online instant messaging
though many people are just too lazy to replace even ugly default Messaging app, so wet just use it with my wife and parents since I boycott Messenger/Whatsapp, just in case for video calls I have Skype Mingo (it's sad that out of billion people in India it's difficult to find one person which would upload always newest build to apkmirror)