It isn't that hard really.
You're a linux/android parent and your teenage kid wants an iPhone. Will you take their phone every now and then just to check subscriptions etc. ?
Or, each family member has an iPhone with their own account, and no other Apple device. You'll be switching anytime you want to check. etc.
I'm aware of these limitations because I've hit them so many time, while having 5 Apple devices at hand. I get it might be s 80/20 split with it being really simple for 80%. But IMO that's just not good enough, at least not 15 years after the first device launch.
[edit] I'm kinda surprise how the goalpost is shifted from "hey it's easy" to "go install iTunes if you're on windows". I having a website too much to ask really ?