This integration exists, but it’s a choice for the sender and it’s not transparent for the receiver. As a sender, when you select a file from Drive, it default

This integration exists, but it’s a choice for the sender and it’s not transparent for the receiver. As a sender, when you select a file from Drive, it defaults to sending a link, but you can change it to send as a normal attachment. As a receiver, I believe you will see a Google Drive link, not a normal attachment.