This is why tainted installers are so useful as a vector - users are less concerned that an application installer asks for temporary admin privilege. The vast majority of malware doesn't 'crack' a system, it fools the user into handing over the keys.
Processes simply cannot get above their station anymore on either OS, and must ask the user for the permissions they seek. There really is no difference in privilege escalation between OSX and Windows. There hasn't been any DOS in Microsoft's OS products since Windows XP came out, whenever that was (I was still Mac-only in those days).
Perhaps you meant 'VMS and BSD', but that does undermine your argument a little. Re: This oculd be due to the popularity of windows.
