Right now, if I want to use OSM on my iPhone and I search "OpenStreetMap" in the App Store I get various applications under various, unknown names. The closest to an "official" name would be OSMaps, but it turns out even that one isn't official and has no navigation capabilities.
On Android, I don't have a phone to test with but seems like the most popular option appears to be OsmAnd. Again, not only is the name cryptic but doesn't imply anything unless you're already familiar with OSM. "Google Maps", "Apple Maps", etc in contrast automatically imply what the app is for even if you've never heard of the brand itself.
If OSM wants to succeed in the consumer space, they need to release an official, "reference implementation" of a mobile client with an UI comparable to the competition that a layman can understand and use even if they have no idea what OSM is nor are interested in contributing.