Actually you don't need it either with a normal PC, that's just some additional safety measures. But if you know what you're doing and keep your system up to date, there's no real need for it.
Now, that doesn't mean Macs are invulnerable to virus and other attacks, far from it, but since there are very few people using it compared to the "PC running Windows" quantity, there are very few virus made to work under MacOS.