I can say it is difficult because its requirement and its policy. Even if it is available on PlayStore, not all gamblers wont be able to download it directly from PlayStore due it its terms of country restrictions. If there is a poll on which one gambler prefer to gamble between using application vs using browser, I believe most gamblers prefer using browser. Simple fact, most well known casinos is not even having android app.
I agree with what you say, just me, there are others who also want to try using a mobile app for additional features. Also, not everything on the Playstore is safe, so before you can fully use an app, read the permissions first, just accept and accept. Alternatively, the data or pieces of information that may be available on smartphones such as contacts and others may be used for something else, or the system may be modified. It's also okay to have an app with a gambling platform, so gamblers also have the option where they can play it comfortably.