I'm going to ask for proof that most small to medium businesses don't have a Windows domain. Even the ones that are only running on a single SBS server have a Windows domain.
Of my 100 or so small business customers, maybe 20 have a Windows domain (defined as having a domain server that’s adminning the domain). The rest just have peer workgroups and *maybe* a file server.
Most small businesses I have worked with use peer-to-peer networking. Before I arrived on the scene, most of the machines were running at administrator level, did not have passwords (or if they did, at least one machine's password, if not all of them, was "password," the network name was usually "workgroup," and they had no idea what a firewall was. If they had a hardware router, the router administrator name was "admin" and the password was also "admin."
The usual reason I was called in was because the computers were running slower than molasses in January, often took a half hour to finish booting and then were almost unusable, and the browser home page was something you would not want your children to see...