As a DM I like to own the physical copy of my D&D books, but I also use roll20 for my group games. The one thing I don't want to do is purchase a physical copy of the books i.e. Curse of Strahd, Tomb of Annihilation etc. and a digital copy. It would just be too expensive for me. I would like to be able to purchase just the maps and player handout for my games but not pay the price for the entire book all over again.