That may have been part of the original motivation, but I didn't see any indication of that attitude in the few resources I checked. The position seems to have come from examination of the evidence, since nothing in the Judeo-Christian worldview requires that all (or even most) DNA be useful.

I did see numerous sources where evolutionists, however, strenuously denied that there could be any purpose to "Junk DNA", for two main reasons. Firstly, it seemed to be an effective apologetic for them, related to the discredited "vestigial organs" argument, which, even in its heyday, had only emotional value. (This is for two reasons: 1, It is impossible, even in principle, to state that a given organ or stretch of DNA is useless -- one can only say that no purpose has been discovered, yet; and 2, Even if an organ or some DNA was useless, this would only make the creationists' point that we have lost capabilities since the Fall of Adam, and would adduce no evidence that naturalistic processes can add information.) Secondly, a genome as large as ours with the mutation rate we have would suffer "error catastrophe" in the millions of years we've supposedly been around if all of that DNA was purposeful.