"Never let an abuser take you to a secondary location": It's OK to offer an app, but if a site is pushing, pressuring or forcing you to get one, it's almost certainly because they want to do something abusive that they currently can't.
Installing an app is a matter of trust; trying to push me to install one against my will is the best way to demonstrate that you should not be trusted.
(Interestingly, I've heard a stance from technically well-informed iPhone users that don't see an app install as a large trust decision, because they assume that iOS is actually decent at protecting their privacy and rights in general. I don't know if that's true; on Android it certainly isn't.)
> It's OK to offer an app, but if a site is pushing, pressuring or forcing you to get one, it's almost certainly because they want to do something abusive that they currently can't.
Every UK bank is, IME.
> Android
I mean if you use Google products it can be assumed you don’t care about privacy anyway.
I'm a mobile dev and know the iOS ecosystem quite well, i can assure you that iOS APIs are locked and developers can access very little user data without user consent. What an iOS user is vulnerable to is fingerprinting (not too different than what happens on web tbh) and 0days. But given how valuable iOS 0days are it's unlikely they are used inside large scale generic apps and not for targeted attacks. Also it's unlikely that a random company sits on a 0days and uses it against its users.
So ultimately yes, installing an app on iOS is not a trust decision because the dev are very limited in what they can do. The biggest trust decision is toward Apple that might have private secret APIs allowing them to do things developers cannot. That's a possibility, but overall Apple business has never been around ads, big data and users profiling so the chances are not this high.