In North America at least All Trails, Gaia GPS, and Cal Topo are three of the most popular apps for hiking. The default basemaps for all three are OSM based and do not display route relations*. I don’t know how popular these apps are in other parts of the world, but their maps cover the globe so I imagine they are used outside of North America as well.
*edit: actually I think GaiaGPS does use route relations to display certain well known long distance routes at low zooms. They aren’t differentiated at high zooms though.