I think that you have to remember that there is still a stench on NU from two years ago and honestly from a few of the games last year as well. To kids that are 17 or 18 all they know is the craptastic job BC did and that Bo is the new coach who had an okay season in their minds. Right now, lots of these kids are basically cold calls and cold calls dont hit a lot.
It will take one more season of good football, lots of tv games and talk in national media to change these cold calls into something more. My guess is that right now the letters from Nebraska end up in the same pile as the letters from Arizona, Vtech and WVU end up. The second level of recruiting right now compared to Florida, USC, UT, Bama and the likes of those schools. It will get there, it just takes time.