Plus, what if an idea is already perfected?
Or it is lacking one finishing touch? Like these spiderbots have alot in common with an ED-209 or battlemech from the torso up, but their lower profile and more numerous legs could make them more realistic for an AFV of this size.
Another viewpoint is that people don't always want to be bombarded with completely original ideas, that some things grow on them over time and they like them more and more. FOSS games have often been a way to bring those things back, after they've been milked for all their commercial worth or simply forgotten about by the commercial game or movie industries. At this point, they probably won't be making a Sixth Element.

Not to say really originals ideas aren't really cool and worth exploring either. I personally like to make models and such from both original and less original ideas; I don't set limits either way.