Two reasons. One, native apps are not needed as Verified Sailor is simple and easy to use. To make Verified Sailor feel like a native app on your iOS/Android hand-held or tablet device, sign in to Verified Sailor on your device and navigate to the home screen. From there add a bookmark to your home screen and your iOS/Android device will create a native app for you.
Second, the fees charged through app stores are as high as 30% and we are doing everything we can to keep the Verified Sailor fees as low as possible. As there is no splashy user interface or interactions required, there is no need to add another 30% tax to use in-app payments. Besides, the Verified Sailor protocol is an open protocol, and anyone may build their own user interface. Check out the Developer docs if you are interested in embedding Verified Sailor into your app!
Check out this article for more information on how to turn your favorite web links, like Verified Sailor, into apps on your mobile devices.