Microsoft force you to use .Net (of some form) and their APIs because that fits their business model (i.e. ties you to the XBox). They're restricting me from using my platform portable pure C code, which is their choice.You're missing the point. Microsoft makes it technically difficult to write a game in a non-.net language, but (at least as far as anyone knows) it's not disallowed in their developer agreement. If you can get LLVM to spit out .net bytecode that works, then good on you, there's nothing keeping you from using it. There's no clause that prevents you from writing a Lisp interpreter in your game, nothing to keep you from auto-generating C# from template files, etc. The only reason people don't do these things is that they're a pain in the ass, not that they would be in violation of the developer's agreements that they signed.
Certainly attempting to achieve developer lock-in is part of good business, especially in the world of game development. But make no mistake, Apple is in uncharted territory here: rather than trying to get people locked-in by providing a smoother workflow with their toolset than they'd find elsewhere (which is what Microsoft does with .NET), they're declaring that all other tools, better or worse, are strictly prohibited.
They're making choices based on what they think is best for their platform, and letting the market chose. This is how the free market is supposed to work.
Bundling IE with Windows without any option to replace the browser is what would be best for the Windows platform. A "plato o plomo" acquisition/sued-to-death strategy employed by would-be-monopolists to kill off competition before it's big enough to compete is best for the business. Gauging prices in a market where a near monopoly exists is "best for the platform."
What you're really hinting at is a discomfort with the entire idea of anti-trust legislation, another discussion altogether. Suffice it to say that "let the market decide" would, if taken as mantra, excuse every sort of monopolistic or anti-competitive abuse that we've ever seen, which indicates to me that it's not a remotely valid argument.
In this case, Apple has, with a stroke of the pen, killed off several toolsets that compete with the one that they're trying to promote. It reads like a textbook example of tying, using control over a mobile phone application marketplace to kill off competition in the developer tools market, and it's almost entirely targeted at a single competitor (though there's plenty of collateral damage, as well, Unity et al).
I think Apple may have something to worry about here.