What came first?

A classic chicken-and-egg🐣. All around us.

Does user behaviour design the product? Or does product development determine user behaviour?
E-commerce, ride-hailing, messaging were few of the (pseudo) originals.
Food delivery, travel, ticketing, and even AI clients largely derived from them. They reused pre-developed behavioural models, leading to a superior experience with minimum conflict.

Email, built 40+ years ago, is one of the vintage originals.

Without digital precedents, it 'derived' from physical mailboxes, office storerooms and paper memos.
The technical/design inadequacies of its time restrained the product, steered our experience, and even limited our expectations. For good.

Even the fundamentals: Inbox, Sent, and Drafts ->
They were based off of three physical trays present in an office then. Today they aren't mutually exclusive, but full of repetitions. And yet, they've remained just the same.
We didn't notice, because we have literally grown up with it. Moulded into it. That's the only way we've seen email to be.