#Because I haven't read the Kyoshi book yet so maybe I'll add one more ship to the list

[shinidamachu]

I don't know much about ATLA but based on my objective observation, how Katara looks at Zuko is the same as how Kagome looks at Inuyasha. So I can see why Zutara is still a popular ship even though it's not canon

Thank you, now I can't get this parallels out of my head and... holy shit! You might be onto something there. There's also the fact of them working so well as a team. Their (more than) rocky start. The fact that their friendship is so deep and meaningful on its own.

Also, you should definitely give ATLA a try, though. Not onlly for Zutara, but because the story is really, really good. In fact, I'd argue that the romance part is actually its weakest suit and not as important as the other themes it tried to explore.

As for Zutara, I'd say it is still popular precisely because it didn't become canon. I don't know if you're aware of this but apparently the writers (and couple) Aaron Ehasz and Elizabeth Welch Ehasz, who were mostly in charge of Zuko's character, wanted to go in a very different direction than what we ended up getting, but the creators Michael Dante DiMartino and Bryan Konietzko (they're know as "Bryke") put their foot down.

The rumor is that another season called Book Four: Air was supposed to happen, featuring Azula's redemption, what happened with Ursa, the discover of alive airbenders, Iroh's spiritual journey and so on. They could have taken this chance to develop Zuko and Katara into something... more. But it was canceled in favor of that awful live action movie.

So they stuck with three seasons and even though the Zuko and Katara's american voice actors thought Zutara was going to happen and the Ehasz couple stilll wanted to leave the ending open in that sense, Nickelodeon and Bryke pushed for the end game we got because, and I quote, "children would cry if it didn't happen."

But it's actually more than that. Bryke, two grown ass man, were so pressed over their favored ship not being as popular as Zutara that they not only dedicated a whole episode of the show (The Ember Island Players) to make fun of Zutara shippers, they also made this cringy ass video and played at SDCC 2008 as a joke:

They used fanarts made by their own damn fans in order to publicly take a dig on them for liking Zutara and, not satisfied, straight up told these people, mostly children and teens, that if they thought Zutara should be together, they would forever have doomed relationships. And they thought it was funny.

That's why I have no doubt if Zutara had gone canon, they would most definitely find a way to ruin it for us the same way they ruined most of the end game couples, so this is actually for the better.

The Zutara fandom made these characters' journey and relationship justice in a way Bryke couldn't, because they didn't have the same interpretation of Zuko and Katara as the Ehasz couple did and since they were the creators, their word was final.

So who knows? Maybe the fact Zutara was not canon is one of the reasons we still have so many great Zutara content to this day?