Quote from auriga
The main problem I see with allowing any sub-category (light novel or not) is that you risk creating double standards. If MU were to allow all East Asian comics to be added to the database, why would it then allow only a specific category of novels? What makes this kind of novel so special that it is the only one that gets to be listed alongside comics?
I don't really see a reason to worry about double standards here. Light Novels (regardless of how they are published) are a distinct medium. There is nothing weird/wrong with focusing on certain mediums while ignoring others.
But anyhow, I can answer your question.
This site was initially created with a focus on Manga = Japanese comic variety, later it incorporated Manhwa and Manhua simply because they are very similar to it. And analogous to manga, Ranobe is a specifically Japanese type of novels. Both Manga and LNs are print mediums (nowadays also published digitally) that are specific to the same culture and have large influence on each other.
Another similarity is that both of them combine text and artwork. While traditional novels only focus on text. One could argue that LNs also focus on text much more than on artwork, but still, illustrations are one of their distinctive features.
