Does the iPhone have a disabled chip for FM Radio?
I wouldn't have believed a single ranting tweet, but the UK's Daily Mail also covered this recently - so it's actually likely to be true, for any given value of 'true'
[my own opinions on the Mail's foil-hat, ranty, opinionated style aside…]

The FM radio hidden in your SMARTPHONE: Mobile manufacturers are denying users the chance to listen to radio for free