Hold it. You're saying that a system whose only significant in-roads regarding security have been to purchase competing, security-minded corporations and/or their products - subsequently redefining "security" to "whatever gets us the most customers" - since inception is somehow more secure than a system that was abandoned around the time they were driven out of business by product A?
Yes.
Windows first became popular with 3.x which was an add-on to DOS, then came Windows 9x which included DOS.
But what about NT? You've missed the point that NT has been the most significant in-road to security MS have ever made.
Inbetween Windows 3.11 and 95 MS came up with NT which did have a security model and was superiour to their DOS based line of OSes. MS couldn't make it their main OS for many years because of backward the compatability problems it'd cause by not allowing programs direct access to the hardware and it also required more powerful hardware than most people had at the time.
Now BeOS had no equivalent to NT unless they were hiding it.
You're assuming that they wouldn't make security changes, and that - at least to me - is one hell of an assumption.
Yes.
BeOS would require a complete re-write to implement a security model, because it'd need a different kernel which would've meant breaking compatability with all old programs, which is precisely why MS haven't made restricted accounts the default with Windows XP. MS will probably change this in a few years time once they stop supporting the 9x series or any software designed to run on it.
Now what's easier implementing a security model for BeOS (which is as hard as securing Windows ME) or changing a few default installation options and implementing one on NT?