Here's the issue. While the NBA has many popular players that are household names, if a team does not have one of these players they might as well not exist unless it's the Knicks or Celtics or something. The smaller market teams with no star player are not being watched by anyone but people like me who will watch any game.
In the NFL it's more about the franchises. Cowboys, Eagles, Giants, 49ers, Packers, Bears.. on down the line.. it doesn't matter who is playing for any of these teams the fan base will WATCH...
Even if the team is complete garbage fans wanna see what the young QB is lookin like or how their other draft picks are looking. Also, in the NFL a team is never out of it for long. They could be 5-11 one year and then the next year make some moves, make a coaching change and they are 10-6 in the playoff hunt.
That don't happen in the NBA unless you can get one of the big names.