That is an option.

 But the issue with that is there are no IK restraints, etc
IKs allow one to move one bone and the rest follow realistically.
Also, Armatures allow the user to create a menu system for moving certain parts just in case you can reach/access it easily.

 But possibly the biggest issue is the bending the joints them-selves. Simply parenting objects together requires the user to angle their Point Of View perfectly to make the mesh bend correctly. Where as an Armature contains it's own set of retraint controls that allows you to always bend the joint in a certain direction (in conjunction of the other related meshs/bones) without having to move the Point Of View at all.

For example, try rotating a robot's finger joints after rotating the hand/palm between 45-90 degrees in all directions. Snapping to a Front, Side, or Top view doesn't help because the hand, and therefore the finger, is not perfectly aliagned with that view. So now you have to go through a long process just to get the right Point Of View to move it. And once you move the hand again, then you've gotta start the tedious process over again for the same mesh and as well as all of the other meshes.

So, yeah, I still need the armature