You know, I somewhat think this is because fans distrust the fate of what will happen to futurama. However, if it were picked up by another party which produced smaller amounts and for quality, Futurama could continue forever. (I'm thinking mini-series 4-7 episodes a season).

I think the biggest problem tv-media is the hiatus, the blanks between seasons cause an eraser from the general public. If they good give a consist stream of content, fans would be much more in-tune with it, and less to forget about.