@Mushroom
That also allows me to go back and make changes in a previous chapter before I post another one based on what I have added in later chapters.
An example of this (in the case of those of us who prefer completing the entire story) is in my newest story, The Holes Binding Us Together, the original story was titled Holes to Other Worlds (I know, a horrid title), but near the end, I hit a passage where one character summarizes what caused so many of the protagonist's new 'friends' to gather around and support her. But, aside from changing the title, I needed to add a few references (and a few more personal faults) in each of the characters, so the titleβwhile betterβactually made sense to the readers.
@Puella Magi,
This is all leaning more towards a solution of write it all, and then post chapters on a schedule to maximize readership.
Another benefit to completing the full story before posting is that you're already well into your next book.
One thing I typically find is that once I complete a book, I have to decompress for several days (more like a week to a week-and-a-half) where actually writing anything is akin to pulling teeth. You generally don't want to encounter that when you're posting two or three chapter a week.
But, just as some authors love to write from a predefined outline, detailing what happens in each chapter, many of us are 'pantsers', who write by the seat of our pants, knowing where the story is eventually going, but we're unsure how the character will actually get there. Neither the pantsers nor the plotters are wrong, just as the post-each-chapter-as-you-write it nor the complete-the-entire-book-before-posting is 'wrong'. It's just that some people work better one way than they do the other.