I don't think the fear of concussions is as prevalent as people think. Yes it is an issue but I think a lot of people understand that the game of football is safer than ever before. I think the biggest issues impacting football numbers are:
1. Technology and Media, we live in an instant gratification world, with football that doesn't always happen, and this isn't just football, this is all activities, all sports, and fine arts activities have lower participation then 20 years ago.
2. Specialization, so many kids think they are D1 in a sport, when most aren't and so many D1 basketball or baseball players actually play football because they are great athletes.
3. Football is hard at any level. I am not saying other sports are easy all can be hard when played at a high level. But football is harder for middle school kids then a sport like basketball, anyone can get lucky and make a shot once and a while and feel good about themselves, football doesn't offer the same. Cross country is an everyone participates sport where most of the race you can hide because you aren't necessarily in front of a crowd. How often at a XC meet does the last place finisher get cheered to the finish line like the are good, when they really aren't.