If you had a number of handouts or pictures to show as part of the game to help set the tone or scene, then I could see using one - particularly if you already have access to it and wanted to make use of some of its value. But we certainly got by playing Masks with just a Discord server. We had voice, we had video, we had a dice roller bot, and we had the ability to share graphics. We never really needed a map, though in a case or two, particularly the confrontation with the villain The Maestro at the Wonder Kidz boy band concert, one could have been useful just to help visualize where the action was (between animated tubas, the collapsing stage, and the crashing heroes at the sound mixing board).