Why should Apple have to do this? If you are a small developer, you can't still market your game or app on social media? You can still do all the marketing you want. You could even give the game away for free. But let's assume you want to make money without selling it through Apple. Create your own web site, market the game, let Apple distribute it free of charge. The first level plays, but when you get to the second level, it wants a code. You like the game, you buy a code to play the rest of it.
Oh, but you want that easy in-app purchase model, right? Well, then Apple is the payment processor. They created the security and process and wish to be paid for their service. Heck, they developed the whole platform with the concept of selling a platform which has the added benefit of allowing 3rd parties to share in the revolution of this new personal platform.
Like a DVD. Did you use to buy DVD movies right? Well, part of the money you paid for that movie paid for a royalty on a per disc basis. Every single copy of any movie on any DVD that was manufactured paid a royalty fee. And we do this now on Blu-ray.
Spotify needs to wake up to the fact that all they did was make an app. Apple created the platform from scratch. They created the dev tools, they created the language. They invested in making all this at huge expense. Maybe Spotify should try it. You have heard of Steam? They took Linux, and made a platform from scratch because they didn't want to be on Microsoft's XBOX. It's not so easy to do.