For Superboy, as an example, they were going to do an Archive many years ago, but they didn't have all the comics they needed to go ahead. They had to get comics from collectors to go forward with the Archive, but it never did get done. Eventually they got around to doing a Superboy collection--but it wasn't an Archive.
I think for doing the Doctor Fate Archive they had the same problem, but that did get done. And there's tons of stuff that they haven't done yet, so I doubt that they have good digital files for those. Maybe they have scans, but that's not the same thing as having separate CMYK files for each plate.
Then there's more modern examples. I'm pretty sure they lost a lot of their George Perez stats (I think it was either in a fire or when they moved offices). I believe they had to reconstruct a lot of the George Perez art that they did for the Perez Justice League collection. But not every "visionary" from the high royalties period between 1977 and the early 90s has gotten collected. And since DC has to renegotiate with many creators to put together those collections, I doubt that they have gotten to the stage where they would create digital files for the books. And they have lost the stats for many of these comics.
Us old timey comics fans are increasingly swimming upstream in our demand for collecting these good old comics. Because our subset of fandom is dying out, we are not the once mighty consumer group we used to be. It's a lot easier to put out collections of modern stuff--stuff from the digital era--because that already exists on digital files and they don't have to go through as many productions costs in getting ready for new printings. And all the royalties have been worked out for those books already. And these books appeal to the new generation of readers.
Under those conditions, it's very unlikely that most pre-digital, un-reprinted comics will be saved on good CMYK files for such a time when the publishers might want to make them available. I'm sure scans exist, but that's not really the same thing. And even digital files degrade over time.