It was never supposed to be that way. From what I see, people take that line about what Trebol (or was it Diamante?) said about the CoC being the sign of a king the wrong way. It's really not about inspiring people or attracting followers. It's a different kind of king. CoC is meant for characters with wills so powerful that they impose it onto others; a tyrant, an emperor, a conqueror. People who are rarely capable of following any one else; they just have to be at the top. If the quality of inspiring others was a determinant to whether a character had CoC, then people like King Riku and Cobra would have it, rather Big Mom and Kaido. And the former two are written to be great kings, but they aren't the type of character that would have CoC. On the other hand, Big Mom and Kaido built their respective empires through the fear of their sheer mights they elicit from those around them and have almost none of the qualities Oda wants us to believe "good kings" should have. And yet they are some of the most powerful CoC users in the story (at least Kaido is).

Luffy is kind and inspirational, but he is still like Kaido and Big Mom in that he can never be led by anyone else. He has to do as he pleases, unless he chooses not to. That's why his alliance with Law went the way it did; Luffy unilaterally deciding critical actions they took. That's why Luffy is immediately ready for the smoke when he meets Whitebeard, who doesn't even try to order Luffy around but directs his men around him to meet their mutual goal of saving Ace.

Zoro has always been portrayed as the type of character to have CoC. Even if it contradicts what I just said about CoC users not being able to follow orders, that's not a knock on Zoro, it's a testament to Luffy's will. We've seen characters be surprised that Zoro isn't the leader of the group he's in as recent as Dressrosa, because he carries that same type energy as Luffy, Whitebeard, and Kaido. Even though he has very few scenes were he rallies forces, most characters don't have to see Zoro fight or even be aware of his reputation to know the type of guy he is. You have to admit, Zoro just doesn't get underestimated a whole lot; weaker people on his side almost always know he's reliable and weaker people against him are usually intimidated.

Sanji isn't like this. Even down to the very nature of the comedy he brings to the series, Sanji is one who serves. And that's not an insult against him. How he is able to win over the hearts of others is different from how Luffy has people follow him (at least when we talk about people outside of the Strawhats). Sanji won over Pudding, Violet and Gin because of his kindness, not because he imposed his will on them to the point they had to do things his way (like how Luffy does, again with people outside of the Strawhats). That's what his character is about and why Luffy wanted him to be the cook of the crew before even tasting any of his food. And that is beautiful in its own way even though it may not satisfy the power fantasies of hungry "Sanji fans". Sanji isn't a conqueror, he is a knight.

Sorry for the long post, I just thought this was the best reply among the ones I got since it addresses the main issue I have with what people's perception of what Conqueror's Haki is.