There are very few quality Gulfstreams available for FS thanks to the manufacturer.  They threaten to sue anyone who models one.

I came across this issue a few months back while on a similar search, this thread kind of explains it.

http://www.simviation.com/cgi-bin/yabb2/YaBB.pl?num=1222882710


Shame too, as they are quite nice aircraft.

I have heard that Dassault has the same attitude about their business jets. Eric Dantes was able to get away with it since his was pretty much the first widely known Dassault jet in FS and it was released before they knew about it, but they are apparently cracking down on the modeling of their biz jets now along with Gulfstream.
I think Grumman has gotten antsy about certain historical aircraft too, but I can no longer find those references.

While I cannot speak for the companies involved, this is my interpretation:

It's not that the companies just want money...they don't want third parties creating unlicensed representations of their products.

They have the belief that any FS model of one of their aircraft is a reflection on their company, and they want to be sure of the highest quality, and want to be involved in the design process. Don't quote me on this, but I believe Dantes was at least at one time cooperating with Dassault on the development of a new FS model, but I have not heard about that in quite a while.

Obtaining permission from Gulfstream, Dassault, and other groups can be quite a challenge in itself, because even if you get "permission", it may have the caveat that you obtain a pricey license to reproduce a version of their "product".

So it is partially money driven just because they have the opportunity, but I believe the main concern was upholding the company's reputation as a maker of the highest quality jets. They are afraid that people will form particular judgements about the company due to the quality of any publicly released model.
Whether or not you agree with it is irrelevant....that's just the way it is.

Rich H wrote on Mar 5^th, 2009 at 5:23pm:

There might just be a loop whore, since the USAF owns those planes, and the love to show off those pretty paint jobs when ever they can.


But I do under stand how the parent company would want the best for there product, Ford is like that in racing games. As long as you model it right, and don't show the cabin of the cars being crushed in a crash you can model it, tune it and crash the hell out of it.......just make sure the virtue cabin is whole, as to not give off the illusion that there cars are unsafe.