Because it is difficult to do.
> If you’re the kind of person who wants to do things that are far out of the mainstream you’re never going to be happy with an iPhone.
FLACs are not the act of an extremist.
No, at this point I think the vast majority of people just use streaming services.
The second biggest group, but probably much smaller, it’s people like me who both have a library and a streaming service.
After that, smaller again, I would assume it’s people who have just a library. The majority of these are probably files bought from Apple and Microsoft and Amazon. Those are all formats that the iPhone can play.
In last place is people who use more unique formats like FLAC. I understand why you would want it over the other formats. But I think it’s by far the least common case.
I find that hard to believe when so many music stores and labels (especially classical music and jazz) are selling FLAC downloads. It all works fine on Android with great polished and featureful apps like "USB Audio Player Pro".
The thing is nobody* does that.
There are a few. That’s why I added the asterisk. But realistically very few people actually do it. Especially compared to the number of iPhones they sell every year.
If you were using MP3 files, you wouldn’t have an issue. Or AAC. There might even be others. Apple really likes to make things easy, but they tend to only do it for the common case. That’s what gets the most use, that’s what makes the most people happy, that’s what they focus on.
If you’re the kind of person who wants to do things that are far out of the mainstream you’re never going to be happy with an iPhone. You can use other apps as other people pointed out. But I wouldn’t expect this to ever work in Apple’s music player. It’s the same reason you can’t have root, re-theme your phone heavily, replace the dialer, or a lot of other heavy customizations. That’s not what they focus on.
It’s just their ethos.