The "answer" button seems to serve to also say "I'm ready to listen" as much as it does to say "I'm ready to say". IMO this kind of goal is better covered by voice messages, or, at least, starting with a voice message. This allows the receiver to pick when they are ready to hear it (including immediately), replay it as needed, and choose when they respond (if at all). Many of these are benefits for the sender as much as the receiver.