Why two different contact are needed?

[happyDuke96]

Hello everyone, when using api channel, agents can send a message through this ip
https://www.chatwoot.com/developers/api/#tag/Messages/operation/create-a-new-message-in-a-conversation
and clients first create their contact, then a conversation, then send a message

and realized that this contact is needed for a conversation session
https://www.chatwoot.com/developers/api#tag/Contacts/operation/contactCreate

but why do we need email,image fields in the contact session, the clients receive a response from the agents and the message is exchanged between the client do not see this contact