Reading long-form texts requires a series of skills, that makes the reading impossible without them.
Reading a fiction book, for example, requires the reader to assimilate the circumstances a character is in so he can understand the context the character is in and why this character acts in a determined behavior.
These texts help improve the memory because, if the reader can not remember the beginning of the book, he will lose himself in the middle of the reading and will never understand the end.
Besides helping the memory, long-form texts help the concentration of the reader. Without concentration, the reader will have no chance of remembering what he just read.
And since we took the fiction reading as an example, fiction books – classic literature, such as Shakespeare – give the readers a better understanding of the reality, because the stories, besides showing how humans are, act, feel, and so on, show how things, in general, are too. That is, what is good and bad, what is moral or not, and what is desirable or must be avoided.