I come from a technical background and have significant experience with multiple operating systems, as well as direct technical support in both retail and business contexts. I feel it’s important to state that I am also a (relatively) long term GNU/Linux user and a proponent of software freedom as described by the Free Software Foundation.
I believe that antivirus software, as massive of a market as it is, exists purely because of major, long-running design and philosophy flaw in Windows.
The approach to software distribution is to force the user to put trust in self-extracting binary packages, many of which are only available from a single source and never audited by a trusted party. This trust requirement, be it implicit or explicit, makes no discrimination; UAC will provide the same warning and require the same escalation of permissions regardless of what is installed. Occasionally, UAC will display information about the software publisher if the installer is signed, but most often this warning is ignored. This kind of process if only useful to the informed user. The average user has no mean with which to differentiate trustworthy sources from the nefarious kind.
On other platforms, most notable Android and iOS, software is distributed via app stores, which are not only gated by an approval process but also audited and kept sanitary by paid employees (at least ideally). On OS X and Linux, many software repositories are kept sanitary not only by dedicated volunteers but also by the community as a whole. This is an approach centered around prevention and mitigation.
In conclusion, I believe antivirus software is a terrible band aid solution to a terrible design issue, and that they do next to nothing to protect end users compared to a policy of whitelisting and plain old education. I would recommend users instead to learn a bit more about their machines and favor platforms that are sound for any of their sensitive work.