Hello! Email doesn't have hierarchical conversations, it's not efficient to add people and get them up to speed with the existing messages in a conversation, and number one: when you open your email, you're in work mode. This does not foster a relaxing chat.
i have personal email and work email. when i open the former i am not in work mode at all. plus meaningful conversations are offen uncomfortable and not relaxing. they dont start with "whats up? how are you?"
That's great, but most people don't separate personal and work email, and even if they do, they still build up a work-related attitude to email that comes across in personal emails too.
Plus, the main issue is that email isn't nicely formatted or hierarchical.
Actually it makes a lot of sense. You can have a deeply hierarchical conversation, with lots of back and forth and branching to separate threads - and yet which only contains two people.