I believe this is because LU is, for the vast majority, platonic. Jojo herself asked fans to not ship the Links together, and the Links are the only main characters. Malon and Ravio show up and are shipped with Time and Legend respectively, and there are, of course, ships with other characters in the LOZ games. (Shad, Sidon, Marin, all of the Zeldas,ec.) But that isn't the meat of the fandom.
In other fandoms friendship/found family content can be pushed to the side in favor of romantic ships, but everybody in the LU fandom is here for found family, even people who aren't aro or ace.
This isn't to say that ace people can't ship characters romantically, and allo people only ship characters romantically.
I'm just saying that people who are looking for friendship dynamic/found family can easily find it in the LU fandom. Also non romantic content is mainstream in the LU fandom, so if you want to create that kind of content you'll get more enthusiastic reception here.
And people don't have to worry about accidentally stumbling across ship fic between, say, Legend and Wars, if they are searching for friendly banter.