I LOVE TO ATTACK!
One definition of uke is "attacker." If there is no attacker, there is no aikido.
Both people need to take on the role of the attacker during the teaching/learning process -- even when showing things to my bar-buddies.
How often do we say, "Here, grap my wrist and I'll show you nikkyo." When we do this, we make the other person, even if he has no aikido experience, the uke, or the "attacker."