Umm..soo when the authors feels sad about finishing the story, why not writing a sequel in...

Its more, unless they're paid to do so(theres a writer and an artist) they cant make more of it as the company ended their pay rent cycle with this particular story.
Webtoons work alot differently than other media, in that it's more heavily monitored by content amount and type and it's also contracted work.

Oh well, I had actually no idea how the work of these artists and authors work, especially when it comes to webtoons...