For most people, movies that focus on the characters is a good thing. But in this case, it was too much about the characters and not enough about the bikes and not enough actual biking action except for the occasional stunt. Because of this, the movie didn't do better than lukewarm with audiences and critics alike since it wasn't at all special, was highly formulaic, and it did even worse with actual motorcycle enthusiasts. Hell, most RL bikers seem to talk about "Wild Hogs" far more than "Biker Boyz".
For the TFATF series, they hit gold because they also focused on the cars and the engines, mentioning several actual models and even mentioning the 2JZ engine by name which 95% of the audience probably had no clue what it actually was but were still able to figure out that it was special somehow. In this movie, if they mentioned even a single bike make or model by name, I can't even remember it. And the action in TFATF was legit, if stereotypically overblown in Hollywood fashion but at LOOKED great, while BB's action was just a few seconds of stunt riding, choreographed kickstand dropping, and a, "Look at this cheesy vision tunnel get looonger!" Very weak. If you didn't care much for the characters, then you didn't care much for the movie as a whole.