Agents are limited by their ability to remember and their sensorium.

An agent without a state can't remember your preferences.

An agent has a "sensorium": the set of signals that it can sense.

It is typically very different from a human; it can be mechanically much larger than a human's sensorium… but orders of magnitude less rich.

This is one of the reasons the Gmail Daily Briefing keeps on nagging you about an action you actually took many weeks ago.

It wasn't able to sense that you did it, and also has no memory (other than emails) to keep track of what you told it you already did.