If you don't think any Rhapsody/Spotify/Napster/Sonos customers purchased an iOS device because their favorite services were available on the go via iPhone/iPod Touch then you are insane. This was a win-win relationship for everyone. Apple sold more iOS hardware, companies like Spotify added value to paid subscriptions.
I'm of the mind that 30% is too much, but I'm not about to make silly arguments, like the one you just did

I'd LOVE it if every consumer were as smart as you'd like to pretend they are. It would reshape advertising and the products we buy. However it just isn't the case. An absolutely insignificant number of people bought an iPhone because it has Pandora. In fact, I would place a large sum of money that the majority of iPhone users don't even have Pandora on their phone. I might even bet, after a little research, that the majority of those with iPhones don't even know what Pandora IS, or that its available for the iPhone.
So while having apps like Pandora is good for the iPhone, please don't mistake a "solid ecosystem" selling iPhones, as "Pandora and Spotify(which isn't even available in the US) is selling iPhones for Apple like hotcakes. It sadly isn't true.
The ecosystem is crucial to the long-term success of the platform. Apple did a really bad job of managing key partner relationships in the past with the computer business, and they are on course to make many of the same mistakes all over again.
Umm... Because the Apple app ecosystem is doing poorly, and declining? Whatever Apple is doing, they are doing it better than everyone else. Time will tell if this is a good move or not. But I don't think that you can argue this is a bad move because Apple has a history of making bad moves
Of course the hardcore Apple cult is going nowhere no matter what the company does.

But Apple is taking a lot of risks. They might be a hip, trendy brand today. But fashion trends can and do change over time. And if you continue acting in the way Apple is so openly and publicly with important partners, they could really sour the image of the brand.
Make no mistake, they are certainly pissing off the content providers. They are however doing the consumers a favor. How? After this goes into effect, if I want to subscribe to something I will
1. Not have to give my personal information to a 3rd party
2. Give my CC information to a 3rd party
3. Subscribe and unsubscribe using my iTunes password, no need to enter all my private information for the zillionth time
4. Manage my subscriptions in one convenient place
And because Apple already has all my information, and I trust them, there is almost zero risk if I choose to subscribe and unsubscribe to a dozen services.
AND, its my choice as the consumer. I can always bypass Apple if I don't trust them, and go straight to the content provider and sign up through them, giving them 100% of the proceeds when I do so. Apple isn't forcing the Consumers hand, they are forcing the content producers hand.
Accounts such as my Netflix one will continue to be billed outside of Apple, so Netflix will continue to get 100% of the money I pay them.'
Again, new and better options for the consumer, but content producers will have to do some adjusting. I'm okay with that.