It is only free for Home/non-commercial use not everyone, no company could survive on that. So others using the Professional version, etc. with much more flexibility and some extra functionality will be paying for their AV solution.
Many as aasgnt said convert to the Pro version.
But Alwil Software have been very generous in their support of the free Home version. avast! is not just free but a very good anti-virus solution, something that is often not considered.
avast! Home/Pro is the most configurable, flexible AV I've used and it provides excellent multi level protection.