AFAIK, gapless playback *is* possible with CD audio. You can have track N flow seamlessly into track N+1 if you master the CD very carefully, such that the cut is placed exactly on the right boundary. So sometimes the cut has to be slightly before or after you want it to be. I have used this CD Writer software to make these: https://www.dbpoweramp.com/cdwriter
I am willing to believe that this was easier for producers to do in the vinyl days, although I don't know the details.
