I am not sure that retraction of strikes is common practice in any MA? Though I could be wrong?? I think WC / KF chain punching is an exception maybe? And but what happens in Aikido is that your opponent, through correctly executed technique will [or should] MAKE you move. If you move BEFORE you absolutely have to, then you are being compliant, which is bad practice. These are the lazy practitioners of Erroneous Aikido that "go with the flow" in a BAD way. Here nobody is served when the two training partners move as though touched by gentle ghosts. This to me is almost disrespectful to the whole idea of Aikido, of training and of MA! I would widen that to encompass all martial artists that practice with that mindset, though I would not digress!!
However, much of this apparent laziness may come from your personal experience, having had a technique done on you many times before, perhaps over many years of practice, you know ahead of time that, say, your shoulder will be dislocated if you do not sink down. Thus you move too soon, before you have to. So, although compliance in many cases is simple lazy and bad training, often it is actually a form of self-preservation [kind of like hitting the break-board softly so as not to hurt your knucks rather than following right through and snapping it]. However, that said, this halfhearted way of training also devalues the training, irrespective of what level those training have reached. Practitioners in this case might as well dance with each other, or go outside for a smoke!
To prove that the Aikido works, nobody moves until they cannot do anything BUT move, then nage is aware of the level of pressure that needs to be applied for his technique to work and uke is aware of his own tolerances. That is the only way to do Aikido, anything else is just flinching and ballet.
Jenna x