I reject the use of voice calls (I actually no longer use a phone) because synchronous communications interrupt what you are doing right now, and more importantly because they lack a proof-of-work barrier. Written communications automatically exclude individuals who cannot read and write properly. That is a fantastic time saver, as it keeps your contact list clean. Furthermore, it is trivially easy to implement anti-spam measures, to exclude individuals who still happen to be able to read/write but whose communications are also undesired. Google/gmail even does that automatically. Written communications are merciless in stamping out and excluding the illiterate and other undesired demographics. Therefore, voice calls are not a feature of a phone, but a bug.