Ways to use it
A child who will not read
A story you argued about the plot of is a story you want to read.
When the book is theirs because they decided what happens in it, reading it stops being somebody else's idea.
They are the author, not the audience
Every chapter starts with them saying what happens. It is their plot, their characters and their ending, which is a very different thing from a book somebody handed them.
Pitched where they actually are
The age band sets the sentence length and vocabulary, so a nine year old who reads like a seven year old can have a story that sounds nine and reads seven.
Nothing is long
A chapter for ages 6-8 is a few hundred words. Finishing one is a thing that happens, rather than a thing that might happen by Thursday.