The problem is, how would an iOS antivirus app even work? In the sandbox model, it's not allowed to scan the storage and memory space of the system or other apps, right? So what is it doing, declaring ITSELF safe? Unless it's using exploits or private API that get other apps banned.
Now, he could release an AV app on Cydia (jailbreak app store), but he's not interested in that bc it's not nearly as profitable.