For me, it's got nothing to do with drive or wanting it enough or anything. He's just not as well-rounded a player as the generation-topping talents. Yes, his dribbling is superb, and he can ping little clever passes around with the best of them. Good, confident finisher too. But he's not lightning fast, so he has to beat a man with pure dribbling - he doesn't really have the option to kick and rush the way Bale or Ronaldo can. He's not got obvious game-intelligence, and his long passing game is nothing special. While he's very good at slipping clever little balls between the lines and behind defenders while at full-dribble, he's not got the vision for Iniesta-esque through-balls splitting multiple ranks of opposition players.
He's thought of as a potential Balon d'Or threat because his best attribute is the one people rate most highly - dribbling. But the sorts of players who actually compete for the honour always have more about them. Iniesta is just as good a dribbler but also perhaps the most lethal assist-maker of his generation, and as good at keeping the ball as any game-running #8. Messi is lightning fast and the best dribbler in the world but also a brilliant passer across all ranges, a scorer of all sorts of goals and has exceptional vision. Ronaldo is a goal-machine and an unstoppable pace-dribbler, but is also an impeccable passer, a physical beast, one of the best attacking headers of the ball in the world and has a huge arsenal of flair and tricks up his sleeve.
Hazard's strengths are just too narrow.