For example, a friend just downloaded the Wayfair app. Why is that necessary? She saved a couple of items, and now the app relentlessly notifies her about things even with notfications off. Doesn't happen with a mobile website.
If you're doing browser fingerprinting and get called out for it, you're the one full of malarkey. Building a web app does not require being shady, just as building a native app does not require one to do nefarious things. The devs* in either scenario choose to do it.
*Devs meaning whoever is behind it whether it is corpOverloards or shaddy devs, a dev somewhere obliged the overloards wishes.
That features like Webgl exist at all is a rage-inducing issue for some people.
The Tim Hortons app doesn't do this. I don't think it sends any notifications at all, at least I've never gotten one and I haven't disabled notifications.
Discounts, freebees, coupons, loyalty club benefits and other financial incentives, usually. Pretty much the only reason you want it, because all these kinds of things usually do otherwise is nag you that you're near one of their locations.