IMO.movies are produced for entertainment and produced to make a profit. Low budget films are not expected to make huge profits- so the investment is small. Generally, movies are made to target a specific demographic. Most films reflect a period in time - only the good ones trancend the mood of period they reflect. Regardless, as entertainment, there is a niche following for the really bad ones. Those neither really good or bad are mostly forgotten. I suspect Billy Jack films fall solidly in the middle position. I doubt that those involved in their production expected much more from them, nor that they would be memorable.