This really is the least concern in the entire mess that is phone network security. (Credit and debit card issuers have the same key distribution and derivation

This really is the least concern in the entire mess that is phone network security. (Credit and debit card issuers have the same key distribution and derivation problem, but it's ~fine, and there are robust standard solutions, such as deriving per-card keys at the personalization site using tamper-proof HSMs.) Even if SIM cards were to feature an asymmetric private key: What would you do with it? How would you look it up, and what would you use it for? There is simply no provision for end-to-end encryption in the phone network at the moment. If there were, it would be a different story, of course, but I doubt that will ever happen.