yeah i suppose but i heard stories that viruses do happen! you probably just go lucky
Virus scanner, even in the Windows world is a waste of time, IMO. They make your machine run slower, many times they interfere with other apps, and when you get infected, guess how much time you spend de-infecting it?
In the computer world, fortunately, we can UNDO, easily! as long as you have a complete copy of your stuff somewhere else. So you don't care what virus you got, you just say GO BACK to when everything was peachy! Easy!
Some people do it with Time Machine I hear, Apple built-in backup mechanism, but sounds like it would take too long to restore, I have no patience, so I use Carbon Copy and keep a known-to-be-good copy of my stuff in an external drive. In case of trouble, I restore from it and am back in business in 15 minutes. No stress, don't care about what virus and whatnot. This also works for bad updates, half-baked apps etc. It happens, not all latest updates are the greatest. No like? Pull out that external drive, restore, BAM!
This is not as same as data backup, you should have a set of data backup somewhere, always, separate from this procedure.