I believe that making real dry transfers, like storebought decals, is a silkscreen process, using photolithographic silkscreening. While I have seen some simple silkscreen kits for crafts use, these are not photo-type silkscreens and you'd have to be an exceptional artist to make them look presentable. I also do not know whether the wax or adhesive is silkscreened during manufacture, but guessing it is.
My guess is setting up that level of silkscreen production is not that practical for the home hobbyist, whereas the making of inkjet decals is quite practical.