John Gruber thinks Apple probably refuses to allow those cases: "But Apple wields its MFI control in other ways too. In a Twitter thread Wednesday, Nilay Patel

John Gruber thinks Apple probably refuses to allow those cases: "But Apple wields its MFI control in other ways too. In a Twitter thread Wednesday, Nilay Patel pointed out there has never been an MFI-certified battery case with a headphone jack. This almost certainly is not because no one thought to make one, but rather that Apple will not approve them. Apple clearly thinks external battery packs (connected to iPhones via a cable) are a better solution than cases with integrated batteries. With Lightning, they can effectively control this. If the iPhone were to switch to USB-C, I don’t think they could stop anyone from making USB-C battery cases. I do not think Apple will cede this control." https://daringfireball.net/2018/11/third_party_usb-c_to_lightning_cables https://daringfireball.net/2018/11/third_party_usb-c_to_ligh...