I mean, money's the baseline, but it's never just that, is it? It's the show of respect. A don who remembers your kid's name, sends flowers when your mother's in the hospital, throws a huge wedding for your daughter. That stuff builds a personal bond that a paycheck can't. You feel like you're part of a real family, with all the obligations that come with it. The threat of violence is always there, obviously, but the guys who last are the ones who make you want to be loyal, not just scared into it.
Look at the old-school guys in books like 'The Sicilian' or even 'The Godfather'. Vito Corleone was a master at this. He did favors, created debts of gratitude that were more binding than any contract. The loyalty became a two-way street, at least in appearance. A don who only rules through fear? He's creating a lineup of guys waiting for him to show a moment of weakness.