Well in the US it used to be civilian helicopters came from military contract offshoots, 204,205,206,407,MD500, FH1100, S70, B234 etc etc
That way the costs were shared.
Now it's going the other way a little bit.
If you're wondering why there haven't been any "new designed" aircraft since the 70s it's because between uprated engines and huge developments in avionics and weapon systems there wasn't a need for a new airframe.
That's where the missing link is, the technology is in the systems not the airframe..
Just look at some of the European junk being touted as next generation..NH-90 anyone..
Apache is still the best attack helicopter in the world, better than "newer designed" Eurocopter Tigers and Agusta Mangustas. Why is that? Because of avionics, weapon systems and power.
The UH60 is still the industry standard in medium size troop transport.
Oh yeah and an EC225 is developed from a SA330, an EC130 is a late model Astar, an EC155 is a SA360 and an EC145 is a BO105.
1960 and 70s technology designs..