>>78399885but you can tell full stories within an episodic formula. It's common in american media because writers move from show to show on a regular basis. It makes it way much easier to get the new guys on board than it is for something with an over arcing story.
I'll exaggerate as an example. If you were a writer, you'd have a much easier time getting on board writing for the simpsons. Homers dumb, marge is nagging, barts a trouble maker, lisas a know it all, maggie's a baby, done, you can now contribute to the writing of the show by watching a handful of episodes.
now lets say you were hired as a writer for one piece. You have to know the devil fruits and their mechanics, who the crew members of the 1000 sunny, what islands they visited previously and who they have fought in the past. You have to know who the four emperors are along with who's in charge of the marines at HQ and who was previously in charge, don't forget about colby and heppo too. and a ton of other shit that needs to remain consistent. Enjoy watching over 500 episodes to get up to speed.
if you want more over arcing stories just watch anime or read manga since it's more often than not the same guy working on te one project for it's life span.