I've been navigating using OS maps on my iPhone for over a year now using ViewRanger. To "download" an OS map you still have to pay - ViewRanger license the dat

I've been navigating using OS maps on my iPhone for over a year now using ViewRanger. To "download" an OS map you still have to pay - ViewRanger license the data from the Ordnance Survey. They charge you so that they can pay OS for the maps. But it's all quite seamless and convenient - you "download" pack of a tokens from the App store, and then "use" them to download map tiles as and when you need them. I'm not sure what an iPhone map written by OS themselves would give me that ViewRanger does not do already. I wonder what their motive is? i.e. why isn't the current model of "licensing" the map data to third party app writers sufficient?