Not every question needs an email. Not every opportunity should wait for another message. Sometimes a two-minute call answers what three days of replies would not.
When communication and relationship information live in different places, context is the first thing to go.
One system, one contact record. Open anything below and keep going from there.
Conversations are how trust gets built. Making them part of the same system as everything else means the call changes the record, instead of disappearing into a call log.