As MarcusT indicated, paper maps give you the big picture lacking on a small screen. I find that invaluable for planning a route, especially over a period of many days. In addition, some countries have detailed paper maps available with a wealth of information which I find extremely helpful. For example, in France, IGN maps have symbols which show elevation contour, roads with beautiful scenery, bike paths, castles, archeological sites, cathedrals, national parks, vineyards, caves, orchards, monuments, foreign military cemeteries, waterfalls, elevation of towns, and several other symbols. I sometimes used maps.me on my phone for navigation purposes, but not for route planning.