MIFARE Classic uses a mandatory, proprietary (presumably still patented) encryption algorithm even for "world-readable" cards, on top of the ISO 14443-3 standard. I'm not even sure whether Apple could legally offer that capability without licensing it from NXP.
On Android, only devices with an NXP chip support these tags for the same reason.
You could argue that Apple could just provide even lower layer access to the contactless interface to allow apps to implement it in software, but I'm not sure if that's feasible (due to timing constraints).
(Note that the article doesn't specify which MIFARE tags it is about. If it's MIFARE Classic, something must have changed, and maybe Apple has licensed the required NXP patents? DESfire should work with iOS without jumping through any hoops, since that implementation is ISO 14443 compliant all the way up to -4.)
