Access to NFC is a huge one. This has a ton of use-cases in for instance IoT and smart home, and Apple limiting access prevents a lot of innovation in that space which might compete with their offering.

Another example is Apple's privileged access to your wifi credentials. Basically this means if you want to share wifi access via your app, as you might want to do in setting up an IoT device, this is only possible if you enter Apple's expensive MFI program.

So in other words, to have a seamless and competitive IoT hardware setup process, you essentially have to enter an agreement with Apple which involves giving them a percentage of your overall hardware sales revenue on MFI devices.