The fact that iOS and Android are the only smartphone OSes did force you to do that.

Unless you mean that you could have made a competitor, but that's inane -- that's a completely different market, with huge barrier to entry.

Apple is using its huge market position in one area (smartphone OSes) to give itself a huge advantage in another (music apps). That's the sort of thing companies have got huge fines for in the past, or were broken in parts for.

You can have alternative app store on Android there's no technical limitations, right ?

And at some point you could jailbreak iPhone and iPod Touch and crack apps but no real alternative market rose up