There are very smart hackers out there who can hide shit, privledge escalate, and even get into your linux boxen like no tomorrow and hide from rootkits.
Very smart hackers will not be deterred for a minute by generic consumer antivirus.
I've not run AV since about 2000 or so... had a couple of infections, nothing serious, easily cleaned. If I'm worried, I'll boot off a CD to check the filesystem... very few things can get around that. I constantly have to clean some of my extended family's systems, despite them running up to date AV. Antivirus does not help most of the time, that's the point.
I'll repeat : Antivirus does not stop you getting infected. Saying that you should use antivirus because otherwise you might get infected is like saying you should wear a purple hat because otherwise a tiger might eat you. They're not related.