American? umm.... lets see, media in general being milked... Final Fantasy, Dragonball (Z/GT), Megaman ( a total of about 30 games including spinoffs) damn, most anime serieses last way too long. In conclusion, why do producers, not just American, milk things. and the answer as all have put it, money. When a show catches serious fans, there is no reason to kill the chicken who lays the golden eggs. If enough people don't like the series in question enough to keep watching, it dies. Dont blame the producers, blame the consumers.