Why are one dimensional players like Dominique Wilkins, Adrian Dantley, or Reggie Miller (all of whom could score, but didn't do much else) good enough for the Hall of Fame, but a two-dimensional guy (defense and rebounding) like Rodman doesn't get consideration? Is it because offense is sexier than defense?
The HOF doesn't reward great players - it rewards great careers. Reggie/Nique got in, not just because they could score, but because they did it at a high level for a long time. Was Reggie a great player in a vacuum? I think that's debatable. Was he able to maintain his level of consistent production for a longtime to accumulate numbers? Yes - and that's why he's in the HOF.
Also, Reggie wasn't a one-dimensional player. Nique either. To be able to score like he did, with his size, is difficult. He did it with more than a three-point-shot, other wise, he'd be Steve Kerr.
Aside from that fact - can you make a credible argument that Rodman was ever a top-20 player in the NBA? Maybe - but it is probably indisputable that Miller/Nique were always top-20 in their primes in the league.