[tsujp]

Understood, but in this (hypothetical) example his mother probably doesn't know exactly what angular velocity or torque are, so making things even simpler with a laymans "power" serves to get the point across.

One could include torque in the explanation to which the follow-up is probably "what's torque?".

The simpler one goes for that initial understanding, in most cases, the less technically correct one is; by design that helps the newbie learn and build up to a more technically correct understanding later on.