But their users do... most I know don't even run AV protection.
There are no Mac viruses in the wild, no self-propagating malware, so the odds of getting infected are very low. People without antivirus are just playing the odds that they won't be among the first to get hit, and given that those odds are probably millions to one, it's not too bad a bet for most people.
AV sellers have been hyping every proof of concept (some of which they probably create) to boost sales, and so far nobody is listening. Only expect OS X AV sales to go up when there's actually something out there to worry about.
Nope - sure don't. Don't intend to. Built-in firewall is the closest thing.