It turns out the humanoid shape when making a general purpose robot is useful because humans have designed all the things around us, for humans.
If a robot were to reach an AED without frying it with magnets, it would need to be tall enough and have fingers.
I agree with you that there are more efficient shapes out there (like the robot from interstellar) but a humanoid at slightly shorter than the average adult (for fear related reasons) shape is the best general purpose shape because it is so backward compatible in all sorts of not yet imagined emergency scenarios.