Still, the (weak) defense here would be no one bothering to attempt them for anything other than i386.

The real defense is that it is trivial in Unix to be a superuser for tiny periods of time and run only one or two processes while doing it. Windows often forces you to be a superuser for extended amounts of time, and, in fact, it is often vastly easier to do even simple things as a superuser than bothering to set up your security correctly, especially for a home user, since Windows' initial security settings are a joke.