Apple's Security Model
/Apple’s doing a lot right when it comes to security: GateKeeper, app sandboxing, and so on. Could Apple keep OS X even safer by pulling a Microsoft and outsourcing most of its security to third-party antivirus companies?
No. Lack of necessity for security software (and the software/battery drain they provide) is a big part of what makes average people feel safe buying and using a Mac over a PC.