The AI is bad at sieges

[Brenador]

I have noticed that the AI rarely, if ever, takes fortified cities by siege. Usually, they send their melee units in suicidal attacks against the walls rather than bombarding them first with artillery. They also are not very good with artillery. Do you experience this problem?

Also, have any of you lost a walled city to an AI player?

Note: I play on Emperor level.