Madden has the same problem as FIFA. There's no competition on the market because EA bought all the rights. So the games are essentially the same each year, just as money grabs for the pay-to-win modes.
I don't think EA would ever make a volleyball game though, it wouldn't earn them the same amount of money
I mean, I kinda agree with the original poster. Volleyball is actually a VERY popular sport worldwide. Poland, Italy, Iran, Thailand, Japan, Korea, Brazil, Argentina, Peru, Russia, Serbia...the level of competition in both male and female volleyball is becoming better and better, so we also have totally new countries (like Slovenia) joining the scene.
According to Google Trends, when it comes to popularity of Olympic Team sports during the last 5 years, only Football (obviously) and Basketball are bigger than Volley. People were generally searching for more info on volleyball than on Ice Hockey, Handball or even Rugby. look here
I think if they developed a Volleyball game, it would actualy sell pretty well. I mean, if they find baseball or even NCAA games affordable, why not volleyball?