And for years, it was our most requested feature, by far. We had instructions for how to pin the site to your home screen, and would explain to users how the website does everything an app can do. Still, constant requests for an app. Finally we relented and released one, and very quickly around half our mobile traffic moved to the app without us really trying to nudge people at all.
People just really like apps! I think it suits our mental model of different tools for different uses. We've also found that app users are much more engaged than website users, but of course much of that will be selection bias. Still, I can see how having your app on someone's home screen could provide a significant boost to retention, compared to a website they're liable to forget. For us now, that's the main benefit we see. Certainly don't use any additional data, though I won't argue that other companies don't.
Piece by piece all of the app was replaced with web views for the website, and keeping the native tab menu at the bottom. No money was saved, but at least they didn't have to update the native parts of the app as features stopped working because of legacy systems being shut down. They kept the native mobile devs and fired some of the web devs instead to save money. Even though the website now needed a browser version and a slightly modified app-friendly version. No biggie, but it complicated the testing, as the responsibility for most of the app was moved to the web teams.