1. Facilities - Nebraska is as good, or better, than most, and continues to invest in facilities. AD didn't have to break the bank to do it, either. Not only football, but basketball, baseball, volleyball, etc. facilities excellent.
2. Academics - Nebraska isn't going to impress anybody looking for an Ivy education, but they used to have one of the best academic support units in the country. That means all student athletes have advisers, tutors, study lounges, labs, and all the help they need to be successful. Not just an assistant coach checking in once a week to see if they turned in a paper or not.
3. History - History has always mattered in college football, and despite the NFL-ification of the game, it isn't completely gone. So recruits don't remember Nebraska being great? They can see crystal trophies, conference championships, and Heisman Trophies. Recruit impressed by Florida, Florida State, Texas, or Clemson's history? Nebraska's is better. In some cases, much better. They're wearing the same uniform worn by Tom Novak, Johnny Rodgers, and Tommie Frazier. They don't know who those guys are, but they will, and it will matter.
4. Location - Lincoln is within a day's drive of Kansas City, St. Louis, Denver, Minneapolis, Milwaukee, Chicago, and other population centers. That means, for at least 40 million people, they can still take off Friday and see their kid play on Saturday in Lincoln. Not as high as some other schools, but good enough that Nebraska should be able to recruit the Big 8 Conference region and Western Division of the B1G without it being an issue.
5. Area talent - You sign the 5-8 scholarship worthy recruits each year and fill in the gaps around them. I'm guessing quite a few schools would have loved to have Noah Fant this year. Nebraska fans often discount local guys because they didn't play in a big city. Joel Makovicka was from a town of 300 people and that didn't seem to be an issue for him. I remember him knocking a lot of big-city kids on their pampered butts.
6. Fans - Texas has been giving away tickets to games this year. My employer got 100 to give to employees free because the stadium was going to be empty for their last home game. Don't assume other schools have the same fan support Nebraska takes for granted.
10. Coaches - not lately, but hopefully soon...