One thing that email is not the best tool for is back-and-forth dialog. Once an email thread got to be a certain length or spans some number of days, it becomes difficult to follow. The increased roundtrip latency is also unfortunate.

Although the alternative to that is not necessarily voice calls. Text chats would have been great, but which platform do you use? Everyone has got their own instant messaging systems these days.

There is also the perception that voice calls have a reduced likelihood of leaving a record, which is why some people are only reachable by phone.