How much appeal does an iPhone lose though if it doesn’t have Facebook?

Probably 3x more than it does with Facebook.

iPhone is useless without Facebook’s Instagram for most of the regular people.

If that's true, then Apple should make an Instagram competitor (like it did with Google Maps).

They have some leverage- if Apple starts banning all the apps people use they'll be furious.

Facebook could make news that's negative of Apple trend more than positive news.

Are Facebook and Instagram unusable on mobile Safari, which bypasses the App Store? (I haven't used FB/Insta for years, so I'm not asking a rhetorical question here: I really don't know and I'm genuinely curious.) I do know that viable mobile browser video games that bypass the App Stores are currently impossible to do on both mobile Safari and Android Chrome because I recently tried. Dark patterns are employed, including adding a typical 300ms audio latency to the Web Audio API on Android Chrome[1], and making WebGL perform terrible on iOS Safari, preventing WebGL from going full screen, preventing accelerometer/gyro input "for privacy reasons" etc.

[1] Superpowered Android audio latency test database shows how awful Android web audio latency is:

https://superpowered.com/latency

Facebook might not make Apple any money via App Store sales, but it does via sales of iPhones. If Facebook and Instagram disappeared from everyone's iPhone, a bunch of people would suddenly switch to Android.

I use Android but I would feel tempted to get an iPhone if they did do that.

Just to confess - did use Facebook in the early days but I've been clean for 10 years.