Both Apple and Android smartphones come with a built in location service, which also has GPS. Firefox OS, which might have needed this service, is no longer around.
Desktops and laptops are rarely used for navigation - the only uses of the geolocation api for desktop web browsers I've encountered are when you go to a retailer's store finder page, and they have a button to use your current location. And even then, the geolocation api is competing with IP geolocation (which doesn't show the user an ominous consent popup)
And I don't imagine it was easy for Mozilla to get quality data - if their service is mostly used by the most privacy-focussed users, I don't imagine those users were lining up to submit their geolocation and wifi data to a public database.