The size of the school districts still pale in comparison to bigger cities outside of Iowa. So obviously population still plays a big role.
I think there's something to be said about kids now days not putting as much emphasis on sports. Heck, in the 10 years it's been since I graduated high school things have changed drastically. My older brother and I were practicing year round for football (speed training, weight lifting, mandatory track practices). That was what all of the cool kids did at our school. They were football players. Even if you weren't a great player you went out for the team.
Now, we have a little brother who is 16 years old and it's been several years since he played any sports. His passion is video games. Which, as older brothers, is hard for us to relate to, but the kid does get straight A's and wants to be an engineer so we can't exactly be hard on him about it. I think it's fair to say there a lot of kids like him today. Both my older brother and I had opportunities to play football at the D3 level, and I don't think there's any reason our little brother wouldn't have had he put in the effort it takes to play high school football. He just didn't have the desire to.