I think Impreg defense is a great concept that i can't believe nobody has copied in the 6 years its been since it came out.
I'm just upset that nobody has copied the gameplay style and setting.
Mainly because all this passion and enthusiasm towards flash-player are quickly going down especially nowadays.
2. Mechanics - artists are usually suck at any "techy" stuff due to their "artistic" nature and not really welcoming towards cooperation since this may ruin their "idea". So they don't really want to mess with some unknown concepts and usually picks up something that is well known and simple(possibly). That's why there is a lot of PvZ like games(linear enemy path, 1 direction of attack) or Breeding Season like games(count by yourself... you can start with Breeders of Nehelym).
Making them put their fingers into something that is hard and unpopular is almost impossible.
3. Quality - Name me at least one western 3D porn-game which has at least the same model quality like in those numerous HQ videos.