They build an app because apps.
Then they compare behavior between app and website.
And there's a stupid, stupid analytics datapoint that shows "Users of the app browse/subscribe/follow/post 2x more!"
That only happens because the only people willing to download and use the app are the power users. But they just worked hard creating an app, and nobody questions analytics data that tells them their hard work was worthwhile.
So now, armed with their supporting data, they begin pushing people to the app because they think it will lead to more pageviews/subscribes/follows/posts and eyeballs on ads.
Using the web version of the product is disadvantageous from the developer's POV as it gives a lot of control to the user over what personal data of his can be shared. Web browser extensions also allow the users to block ads and other annoying content -- this is sub-optimal for the company as it trims their ad revenue, and as a result, potential future advertisers.
It's all about controlling what the user sees based on data collected from tracking, imo.
Apps have much wider permissions off the bat and can request more as necessary.
I'd assume (though I have no data to back it up) that your service would get used more if the user has an app downloaded as the barrier to access your service is much lower
Unblockable Ads, In-App microtransactions, Push Notification-based variable reward schedule reengagement dark patterns are the result.
The app will auto-update, so as new features/tracking/things are desired, they can push these out to devices.
Basically, they get more control of the end user.
Although i wonder how many app users only real benefit from the app is a button to launch the site from the home screen, and how many of those users would switch if they were aware of how to add a browser bookmark to their home screen. Anecdotal data, but I have had several friends with this problem, two specifically complaining about the reddit app being less readable than a browser but wanting a single button to press to launch the site.
This isn’t adding value to my life. Notifications are an infestation of advertising into every untouched aspect of our personal lives. If I turn them off, I get fewer ads. If I get fewer ads, I’m less inclined to consume and waste money on things I never needed, and save that money for the stuff I care about.
Instead of being restricted to a browser, you are on their device, with whatever access you want.
(I'm not sure exactly if this is the present motivation. But it's the motivation for a lot of apps. Data can be sold / used for ads when collected in very large numbers, and apps collect more data than websites. So there are strong business incentives to move to an app, for many sites.)