Honestly I'm not sure this is necessarily a thing these premium creators do deliberately to maximise how much cash they can squeeze out of their audience.
Obviously there are definitely people out there who are like that, don't get me wrong! But when you talk to amateur webcomic creators, something that comes up a lot is the sheer length or scope of what they have planned out. It's often absolutely ridiculous, because what a lot of us want to make is something with the scope and detail of our favourite manga series or ensemble cast TV shows, but we maybe forget that we're solo creators making 2 pages a week not... you know, 22 pages a week like a mangaka with assistants. 
Something I know about long running popular series from hanging out with people making them is that after a certain point, your comic's longevity often starts to weigh it down. You'll get diminishing returns, your subs and especially engagement will stagnate. Worse, your comic might start to look and feel dated as words you used early on fall out of fashion or become problematic, or your depiction of marginalised people that everyone said was good is now no longer up to the expected standard. Worse, a lot of creators I know with long-running series in page format have had a big panic over the increasing dominance of long-scroll format and how their work is no longer optimised for how people now consume comics on phones.
Honestly something noteworthy about a lot of Tapas' localised Kakao titles is that they're often quite short. They're written like a short, standalone series. It's worth noting that these are largely comics made by seasoned professionals; a full studio team with a writer, editor, artists and assistants, so it makes sense they see the project as a managed product rather than what a lot of series that start free to read and then go premium are, which is one person making "a cool thing I want to make!" that's often one of their first comics of this kind of length.
Sometimes creators bite off more than they can chew. Magical Boy is an example. It wraps up a bit quickly at the end and it feels like certain character and storyarcs were cut short specifically to avoid this problem. I know I personally have cut an entire arc out of the planned story of Errant and seriously reduced the role of some characters just to keep the story manageable! It's so easy for things to get out of hand when you have an ensemble cast you really love!
